First step in the process is to create a new ICP in the MBG Configuration TAB with an IP Address which is not valid on the network and name this ICP “Block number” for example.
The go to the Services TAB and select Sip trunking and select Modify against the SIP trunk you wish to add this incoming CLI blocking on and you will see similar to below:-
In this example the SIP trunk has been set up to block incoming calls from 02035909408 and 07948534698.
If nothing already setup then row 3 on above will be row 1. Always use the PREPEND option to add CLI blocking entries as these rules are applied from row 1.