MSAP parameters that are not obtained from a local user database lookup, and that are not returned from RADIUS or DIAMETER can be specified in the msap-defaults section of the capture SAP context (this is a last resort scenario):
config>service>vpls>sap# msap-defaults ?
- msap-defaults
[no] group-interface - Configure the group interface
[no] policy - Configure the MSAP policy
[no] service - Configure the service