iPhone 5 freezes making/receiving calls

[david1990]

I dropped my iPhone 5 the other day and after it the phone started losing service all the time. It would drop the service and then regain it back for itself. After a while it stopped losing service but the phone doesn't seem to be able to make or receive calls. When I try to make a call the phone starts to get really slow, even freezing at times, and I can't hear anything both on loudspeaker or the earphone piece (they both work fine upon testing) the number I'm calling to receives the call but also doesn't hear anything. The phone can receive and send text messages and can access the internet through cellular data fine. What's wrong with it? I sent it to a store and so far, they have replaced the dock with the antenna, the full back housing, the screen, the battery, the motherboard... And it still refuses to work. What's going on? As soon as I remove the SIM card during its call freeze state it unfreezes itsel and works fine. Everything but calls work fine. I can receive calls but when I pick it up it starts freezing again and I can't eat anything. I'm so desperate. I've got no clue of why could this be... Can someone help me?