iPhone 5s t mobile audio issue

Hi all, so I have the iPhone 5s and I love it but recently I've been having an issue with the speakerphone and the ear piece. Videos from YouTube and Facebook play just fine but when I'm on the phone with ppl it cuts in and out and I only pick up every other word. I've taken the phone to t mobile they've plugged it in their PC to check software (that checked out), they changed my SIM card, and then we did a master reset. Finally I had them send me another one ( insurance). Now this phone is doing the same. It doesn't matter if I call land line or cell it's allows the same. Can anyone help out?

How strong is your T-Mobile reception area? This doesn't sound like a phone problem at all but simply a weak or broken signal. T-Mobile is also my provider here in the Dallas - Fort Worth area of Texas, however, their signal is always strong and clear on my iPhone or any other phone I've owned. But... if I leave the metro area and get out in the boon docks of Texas, the signal is weak and spotty. Not much you can do if the signals are weak except to go with another provider. Since your iPhone 5s is not locked and you're not under contract, you can switch to AT&T. You'll just have to continue paying T-Mobile for the phone if you bought it on their payment plan.