Use the Prefix Blocking feature to block and allow outbound dialing prefixes

PrerequisitesClick to expand

Genesys Cloud Voice administrators can use the Prefix Blocking feature to create rules to allow and block outbound calling to certain countries. This feature is designed to prevent unauthorized users from making outbound calls to high-cost international destinations.

The Prefix Blocking feature provides administrators with the ability to control outbound dialing by adding prefixes to either an Allow List or a Block List.

You can allow or block an entire country using just the prefix or you can allow/block certain portions of a country by using the country prefix along with an area code. You can even allow/block a specific number by using the country prefix along with an area code and the full number.

Note: Beginning in June 2026, new and existing Genesys Cloud Voice customers must configure the Prefix Blocking feature accordingly:

For new Genesys Cloud Voice customers, outbound calling to all countries is blocked by default. More specifically, all country prefixes appear in the Block List by default. Administrators can allow outbound calling to specific countries by removing prefixes from the Block List and adding them to the Allow List based on their business requirements.
For existing Genesys Cloud Voice customers, both the Allow List and the Block List will be empty. Administrators can allow or block outbound calling to specific countries by adding prefixes to either the Allow List or the Block List based on their business requirements.

The Prefix Blocking user interface consists of two components: a management panel that you use to configure and test prefix blocking and a list of either allowed or blocked numbers.

Management panel

The following actions are available in the management panel.

Action	Description
Search	Search for prefixes in either the Allow List or the Block list.
Allow List	Displays the list of prefixes that can be called.
Block List	Displays the list of prefixes that cannot be called.
Test number	Simulates a call to a prefix.
Export	Export the current list of prefixes to a .csv file.
Bulk import	Import a list of prefixes from a .csv file.
Remove	Select and remove prefixes from a list.
Add prefix	Add a prefix to a list.

Allow List/Block List

Both the Allow List and Block List display the prefix rules in the table, which has the following columns:

Column	Description
Prefix	Displays the prefix.
Country	Displays the country associated with the prefix.
Country Code	Displays the country code.
Area Code	Displays the area code, if present.
Actions	Provides quick access to the Remove command.

Note:

If the same prefix appears in both the allow list and the block list, the allow rule takes precedence. This means that calls made to that prefix are permitted.

For example, if country code +1, which covers the entire North American range, is added to the allow list, but specific Dominican Republic prefixes, such as +1 809 or +1 829, are added to the block list, calls to these Dominican Republic prefixes will be allowed because the allow rule for +1 overrides the block rules.

To block calls only to the Dominican Republic while continuing to allow other +1 destinations:

Remove +1 from the Allow List
Add specific Dominican Republic prefixes (for example, +1 809 and +1 829),+ to the Block List

You can use the Test number feature to examine similar scenarios.

Using the Prefix Blocking feature

Warning: Changes to active prefix blocking rules affect live traffic immediately. Always validate prefixes in a non-production environment before enabling rules in production.

To access the Genesys Cloud Voice Prefix Blocking feature:

Click Menu > Digital and Telephony > Telephony > Prefix Blocking.

Add prefixesClick to expand

Select the list to which you want to add prefixes: the Allow List or the Block List.
Click Add prefix [ hidden]Icon included[/hidden].
In the appropriate dialog (Add Blocked Prefix or Add Allowed Prefix), do one of the following:
- Enter a number in the Prefix box. You just have to enter the number. The preceding “+” is added automatically.
- Click the Prefix drop down arrow and select a prefix from the list.
Optionally, click Add to continue adding prefixes.

As you add prefixes, take note of any warnings that appear:

A yellow warning indicates that the entry impacts many prefixes. You may want to consider narrowing down the entry by specifying an area code in addition to the prefix.
A red warning indicates an incorrect entry that you must fix before you can successfully save it.

Confirm your entries

If you have added multiple entries in either the Add Blocked Prefix or Add Allowed Prefix dialog, there are several ways that you can analyze and confirm your entries:

Use the Search box to locate specific entries.
Click Show only invalid entries check box to view only those entries that contain errors.
Click Show only entries with warnings check box to view only those entries that contain warnings.

When you have confirmed the entries:

Click Save to add prefixes to the Allow List or Block List.

Remove prefixesClick to expand

Bulk add or remove a list of prefixesClick to expand

The Bulk import provides you with a way to add or remove a large number of prefixes to/from the Allow List or the Block List using the provided .csv template. The template has the following fields and contains a couple of example entries:

Field	Description
country_code	The country prefix. Just enter the number. The preceding “+” is added automatically during the import operation.
area_code	If you want to allow/block certain portions of a country, add an area code. If you want to allow/block and entire country, leave this field blank.
prefix_type	Use this field to specify which list the prefix should be added. Enter either “allow” or “block” in the field.

Download the .csv template

To download the .csv template:

Click Bulk import
Select either Create or Remove. The Bulk Create Rules from CSV or Bulk Remove Rules from CSV dialog appears.
Click Download example CSV.
After the download is complete click Cancel.
Open the .csv file, fill it in, and save the file in .csv format.

Upload a .csv file

To upload a .csv file:

Click Bulk import
Select either Create or Remove.
- Select Create, if you want to add prefixes to the Allow List or Block List.
- Select Remove, if you want to remove prefixes to the Allow List or Block List.
The Bulk Create Rules from CSV or Bulk Remove Rules from CSV dialog appears.
Select Click to upload.
Locate and select your .csv file.

Confirming bulk imports

After the bulk import operation concludes, all the imported entries appear in the Bulk Create Rules from CSV or Bulk Remove Rules from CSV dialog. There are several ways that you can analyze and confirm your entries:

Use the Search box to locate specific entries.
Click Show only invalid entries check box to view only those entries that contain errors.
Click Show only entries with warnings check box to view only those entries that contain warnings.

When you have confirmed the entries, do one of the following:

Click Create Rules in the Bulk Create Rules from CSV dialog to add prefixes to the Allow List or Block List.
Click Remove Rules in the Bulk Remove Rules from CSV dialog to remove prefixes to the Allow List or Block List.

Export a list of prefixesClick to expand

You can export all prefixes from both the Allow List or the Block List to a .csv file, which shows you prefixes in the following format:

Field	Description
country_code	This field shows the country prefix.
area_code	If you have allowed or blocked certain portions of a country, an area code appears in this field. If you allowed or blocked an entire country, this field is blank.
prefix_type	This field indicates which list the prefix came from. Either “allow” or “block”

To export all your prefix rules:

Click Export
Save the .csv file.

Test a numberClick to expand

The Test Number tool allows you to test phone numbers that you have added to either the Allow List or the Block List. This tool simulates the prefix screening flow for a phone number and displays the results.

Click Test number [ hidden]Icon included[/hidden]. The Test Phone Number panel appears.
Enter a prefix or a prefix and phone number and click Test. Just enter the number. The preceding “+” is added automatically.
- If you entered a prefix or a prefix and phone number from the allow list, the Call ALLOWED result appears.
- If you entered a prefix or a prefix and phone number from the block list, the Call BLOCKED result appears.

In addition to the main result, the Test Phone Number panel shows the Screening Flow, which is the process that Genesys Cloud Voice goes through as it evaluates the number and determines whether it is an allowed number or a blocked number.

[NEXT] Was this article helpful?

Get user feedback about articles.