I have an issue with our gsm gateway which i think is codec related. The gsm gateway works for calls made out from the office out using the outgoing rules, ive got all that to work fine. Where it stops working is if the call comes in from outside, hits a desk extension which then diverts via the gsm gateway to a mobile. what happens then is the person on the mobile can hear the caller but the caller cant hear them. its not ports as it works fine when not using gsm ie over a voip transfer. any ideas?!