It is not possible to block incoming calls based on Automatic Number Identifier (ANI), or calling number, information when Media Gateway Control Protocol (MGCP) is used.
When Cisco CallManager-controlled MGCP is used, the only way to block incoming calls from specific numbers (ANI) is to contact the service provider and have them block the number.
Incoming calls based on ANI (calling number) can be blocked with the H.323 gateway.
For information on how to block calls based on ANI (calling number) with an H.323 gateway, refer the document How to block incoming calls based on calling number and called number information with a Cisco IOS H.323 gateway.
For information on how to block incoming calls based on ANI and Dialed Number Identification Service (DNIS) on Cisco CallManager and Cisco IOS voice gateways, refer How to block incoming calls on Cisco CallManager and Cisco IOS voice gateways based on ANI and DNIS information.
You can now block calls using calling party information for CUCM ver 8.0 and up.