Dear, Sayed
I think, that following take place:
1)Lack of MSRn (in VLR) —PRN_err with Cause=No Roaming Number Available—>HLR—SRI_err with Cause(most probably)=System Failure—>GMSC—appropriated announcement or ISUP_Release with Cause=111-Protocol error, unspecified—>outgoing_MSC—> appropriated announcement
2)Subscriber out of coverage (Paging Fail in VMSC)—appropriated announcement or ISUP_Release with Cause=20-Subscriber absent—>GMSC—>outgoing_MSC—>appropriated announcement