Dear, Slimos!
Let call setup fail. But Location update? Fail or no? Any additional info about cause C3.50? For the best if you will indicate the standard cause value for Call setup and Location rejection (if any).
It is possible the following:
1)Call setup (CM_Service_Request) and rejection this message with cause Imsi unknown in VLR.
2)In general case the majority of mobiles makes subsequent Location Update message with ‘follow on proceed’ indicator and without subscriber notice.
3) After succesful Location Updating procedure the Call Setup attempt follows in a general way.