Did you add these callers to your Trusted Callers list?
Login to OBiTalk
On the top left of the page click Trusted Callers
Click the red X to delete the entry and Save
If that doesn't work, use OBi Expert to modify your configuration
Assuming you provider is defined on SP1
Voice Services -> SP1 Service -> X_InboundCallRoute
Remove any rule that looks similar to:
"{(x.8005551212|x.8005551313):aa},"
Both boxes to the right of the value must be uncheck to view or change it
Click Submit