Mobile and Remote Access (MRA) in Cisco Unified Communications Manager (CUCM) enables Cisco Jabber and other collaboration endpoints to securely register with CUCM from outside the corporate network without requiring a VPN.
MRA leverages Cisco Expressway-E and Expressway-C to provide a seamless and secure communication path, allowing users to access voice, video, messaging, and presence services remotely. This improves user experience and security by eliminating the need for complex VPN configurations.

To prevent OffNet-to-OffNet call transfers (which can be exploited for toll fraud), you must properly classify calls and configure restrictions in Cisco Unified Communications Manager (CUCM):
Classify the SIP trunk to Cisco Unified Border Element as OffNet
This ensures that calls passing through the trunk are considered external (OffNet). This classification helps in applying call restrictions effectively.
Set the Allow OffNet to OffNet Transfer Cisco CallManager service parameter to false This setting explicitly prevents OffNet-to-OffNet transfers, stopping users from transferring external calls to another external destination, which is a common toll fraud scenario.