Have you set up a call-forwarding number at the campaign level but the callbacks are still going to your master call-forwarding number?

If someone is calling back from a number that is not in that campaign, the call will go to your master call-forwarding number as the system has no way to know that that number belongs to that campaign forwarding setting.

Also note: we do have a blocker in place that will restrict non-prospect phone numbers from being forwarded. This is to avoid any unwanted calls that may be a result from spoofing.