Here is an example
475 is the extension of the phone and 3475 is the bell.
You add in the parameter GRPCAL into the COS of both phone and bell example COS 12.
ADD-AUN:475,,ONS,475&3475,,YES,NO,NO;
CHANGE-SDAT:476,ATTRIBUT,PARARNGM;
CHANGE-SDAT:3476,ATTRIBUT,PARARNGS;
CHA-COSSU:COS,12,GRPCAL;