in the message CIPHERING_MODE_COMPLETE
what is the actual ciphering mode chosen ?
even if the call is not ciphered, those “ciphering” messages are still exchanged. It is used to choose among A5/0, A5/1, A5/2 and A5/3. MS, BTS and MSC have to all agree on the same cipher.
A5/0 = no cipher.