Phone quits mid conversation

Please help! I have gotten an Android a few months ago. Quite frequently I will be having a conversation with someone on my phone, when the person I am speaking with will all of the sudden say: "I've lost you! I can't hear you!" I can hear THEM, but they cannot hear me. I have to shut my phone off, take out the battery, and put it back in, then restart the phone. WHAT IF THIS WAS AN EMERGENCY????? Is anyone else having this problem, and what can I do about it?