Help Calling Issues

[Fritzel]

I bought a Motorola Spice XT300 in Canada and ran it on Mobilicity's network where it worked perfectly. I recently moved to the UAE and, in order to use my phone on Etisalat's network, unlocked it. The phone sends and receives texts without problem. I am also able to call people and connect; however, I am then unable to end the call. When I receive a call, the normal incoming call screen appears. I slide over the answer slider and the ringing and vibrations stop. After a second though the vibration starts again and if I turn my screen on/off the incoming call screen is back. I am able to reject the calls though. Any advice would be hugely appreciated.