During call voice becomes scrambled (alien like)

My wife and I both have iPhones, her is iPhone 4 and mine is iPhone 5. We live in an area that AT&T claims to have 'Best Service', but we have to use their Microcell in order to make calls. We have been experiencing and issue for quite a while and has gotten worse recently. We'll be in the middle of a call and the voice, of the person we're speaking with, will become scrambled and sound alien like. Up until yesterday, this only happened while at home, but my wife had it happen at her office yesterday. Has anyone else experienced this and found a fix for it? Just in case it matters for this issue, we are also experiencing dropped calls and needing to try multiple times for an outgoing call to go through. Thanks.