4 device replacements in less than 3 months; CSR refused to replace device again.

Hello,

I am currently an AT&T customer since October of 2009. Never had an issue with Customer Support. Always on time and very professional and curteous. However, it is until recently. After I called to complain about the same issue happening with now 4th device replacement (Moto X), not to mentioned i had to spend in total about 50 min of on hold time and call being dropped after I got connected with the service rep, and no call back, Customer Service Rep (2nd attempted call) told me that my phone is functioning correctly after a remote support app installation and she made a few test calls (which wouldnt help the case as the issue happens randomly). Well, I've used this phone 2 weeks now (4th replacement) and since I use my personal phone line for business emergencies, over the last 3 months I have had a lot of angry customers complaining they cannot reach me for emergency, when my phone displays no mentioning of missed phone call or voicemail left. and this happened once before in 2010, and after 4 replcements, AT&T replaced my device to a totally different model, which in return solved the issue. However, now I am being told that they will not send the 5th replacement, because it cant be that 4 phones have the same issue. It must be something else then, not the phone! (Which is crazy, because it cannot be sim card or network issues, since my wife was iphone 5s, and no calls dropped, always 5 bar reception, whereas I'll be standing right next to her and have 1 bar, or NO SERVICE displayed on my phone). It could not be a sim card issue also, as I have replaced my sim card recently, and it have not changed a thing.

I'm at a loss here: angry customers that can't reach me in case of an emergency; pregnant wife, that cannot reach me over my phone unless she uses skype or voxer, and me - not being able to do anything about it, because CSR said that I either get another device through AT&T Next program, or wait for my upgrade in October, because she found no issue with the device and basically did not believe a word i said.

HELP?