Number validation
Set callback number performs some special functions in addition to just setting the number. This component also validates the number. Since we are using the number that the call is coming from, everything should be OK. But there may be an instance where the caller ID was not available, and therefore the system doesn't have a valid number. To account for this condition, we still need to validate the number and act accordingly. On success, we need to connect this output to the Play prompt component that was after the original Set callback number. This connection will add the callback to the callback queue.
For the invalid number and not dialable outputs, we will want to connect these to the same Play prompt component that the original Set callback number was connected to. These connections will capture any issue with the caller ID and request that the user enters a new number manually. Your contact flow should now look as in Figure 9.7: