Have you set up a call-forwarding number at the campaign level but the callbacks are still going to your master call-forwarding number?
It's possible you input the call-forwarding number after the campaign was created and messages sent through it. When we do this, unfortunately, some calls could still be forwarded to your master call-forwarding number as these are the settings into which they were imported.
In order to ensure this doesn't happen in the future, you need to create your campaign and enter the call forwarding number immediately, before you import your prospects. At that point, all incoming calls to the prospects in that campaign should forward to the correct number.