Can't hear just one person through my iPhone 4

Okay, so lets see if this works. So I've had my iphone 4 for about a year and a half, I've never really had issues beside the normal glitching and having calls drop here and there. Recently I've had an issue with my iphone connecting with just one individual. Yes, I know it sounds weird but keep reading. I have been able to make calls and recieve phone calls fine, however I cannot with just one single individual. They to also only have the same problem with me, however the only difference is they can hear me but I cant hear them or anything. We're able to text and send picture messages without any issues.

Now sometimes when I try to call them, itll ring twice and then the line just goes dead, but thats usually them picking it up. I cannnot hear them at all. I've already done the reset on my phone and I've already contacted apple about this issue and their about as lost as I am because it doesnt make sense that this is only happening with one individual. I've also blew out the speakers and such like people have suggested. I use my head phones that came with my speaker, and ive connected and reconnected them incase my iphone thought they were plugged in.

Let me give you a little bit more info. They have an android phone, we have the same carrier which is verizon and they live in another state (not sure if thats helpful). I'm completely lost because this has been going on for about 4 days now and its driving me crazy. This happened a few weeks ago, however it magically fixed its self ( im thinking it was because I had bad service). If anyone has any solutions that might help, please, please let me know.