If we have configured our phone system to forward the call to other extensions if an incoming call is not answered, does the call sessionid change or does it remain the same?

I am currently storing a generated key value, call sessionid and phone number in my database in order to provide a lookup table for existing calls. If a record exists for the sessionid and phone number the existing key is returned, but if a record does not exist we generate a new key.

Recreating this scenario is hard, and my thought is that i am adding a record for the sessionid and when it is forwarded to another extension, it finds the existing key and tries to insert it again.