Stripping of digits and prepending it with another digit/s when dialling outbound numbers, for example, stripping +27 and prepending with a 0, because your provider does not not allow you to dial +27 numbers, can be achieved by logging into the Comma GUI follow the below procedure:
1. Select Start -> Configuration
2. Select Advance menu -> Outbound Routes
3. Select Edit to edit the Outbound route you created under the Outbound panel.
4. Select Dial Patterns.
5. Under Dial Patterns Wizards, edit your current dial plan, by adding the digit/s you would like to be added to number under the prepend section, then adding the digit/s you want to be stripped away under the prefix section, and then leave the dial pattern that is under the match pattern section which was added when you configured outbound route.
The above screenshot of the Dial patterns wizards, will strip +27 and add/prepend 0 to the Outbound DID/number with X. catching the numbers to after after +27 and sending them with a 0 infront.