My boyfriend and I (share an account) both recently purchased unlocked Blackberry Z10s from a third party. He works out of town in an area with limited LTE service. When I text me, it says that I am sending in MMS mode, even though it is purely text messages with no multimedia. When I text other people, it sends as SMS, like normal. He can't receive MMS because of some issue with the network where he's living/working. We didn't have this problem when I was using Android. Help!