Hello!
Simply say :
1)Network >> MS Paging
2)MS >> Network paging_Response
3)Network >> MS Setup
4)Busy MS >> Network – see extract from etsi 24.008-008
“A busy MS which satisfies the compatibility requirements indicated in the SETUP message shall respond either with a CALL CONFIRMED message if the call setup is allowed to continue or a RELEASE COMPLETE message if the call setup is not allowed to continue, both with cause #17 “user busy”. “