T-Mobile USA review: unethical business practices

In May on 2014, I switched from Verizon to T-Mobile. Before signing any contracts I asked one of the managers (J) if I would experience degraded service and coverage by switching. His response was "You won't be able to tell a difference between T-Mobile and Verizon." Well I did! I fly commercially for a living, and I was unable to use my T-Mobile phone in Meridian, Boise, San Francisco, Chicago, Seattle, Ft Lauderdale etc. I was unable to call my maintenance team from the flight deck of the aircraft while on the ground at ANY airport we serve. My kids couldn't call from their bedrooms (Meridian), my wife couldn't complete a conversation while driving 2 miles along Chinden Blvd., and if I walked through my garage my calls would drop. More than half the drive between Boise and Salt Lake City has no coverage, even when you're driving by cell towers. Because it took several weeks to learn about T-Mobile's disgraceful service coverage, and because I'm away for much of the month, I missed the 14-day 'buyer's remorse' period. I brought my phone in and talked to another manager (B) in the Milwaukee store who changed a few setting on my phone and asked me to try it again for another month (which is longer than the buyer's remorse period) and if I was still not receiving adequate coverage he would take back all the phones without penalty, basically extending my buyer's remorse period. I continued to use the phones for several more weeks, however, after fielding many complaints from my family, having to leave my Chicago hotel room and stand in the middle of a parking lot across the street in 10 degree weather in Chicago and watching my texts to my wife queue up without sending (6 of them) while running through the Seatac Airport in Seattle, I had enough. I signed back on with Verizon and ported my phone numbers over, then attempted to cancel my service with T-Mobile and return the phones as promised by manager (B). Manager (B) wasn't in, and I explained the verbal agreement with manager (J) who grinned at me and said: "Did you get it in writing with his (B's) signature." When I responded "No" he smiled and said "Good luck". I confronted manager (J) and reminded him about his "You won't be able to tell the difference" comment. That's when he said: "I never said that. Everyone know that Verizon has better signal coverage because they operate on a lower frequency band. We can't compete with that." The last correspondence I had with manager (B), he told me that he was sending my complaint to a regional manager by the name of Heidi (I believe). I haven't heard from either of them, instead, I've now received 3 phone calls from their collections agency threatening to destroy my credit rating. My problem is that my signature is on a contract, of which I HAD to sign in order to enjoy the T-Mobile experience. They've got me. It doesn't matter that both manager (J) and (B) blatantly LIED to me on two separate occasions. Now they're trying to collect $3, 621.20 for just a few months of service. (see attached). STAY AWAY FROM T-MOBILE ! I can't emphasize this enough. Their unethical managers LIE ! Their service is DREADFUL ! If anyone needs more information, I'll gladly field any questions at [protected].