Being charged for a phone I have returned. Help?

Whats the point of asking for help from tmobile when everyone over there will take their precious time until it goes over to collections. Got fraud by tmobile 3 times. Made me join promotion for free tablet and got charged for about 2 years ( i called alot) ended up paid everything. Also got charged for fraud account. It took really long time to be solved bc everyone told me different information. One rep told me they already filed a fraud. One rep told me i have to send certain documents but they told me one by one. If they told me all the documents they needed in the first place. I didnt have to waste a time kept calling them. Finally last documents i had to send. It was during christmas and new year so i sent it after holidays. They sent it to collections saying its my fault. Lastly, they charged me for returned phone that was more than a 6 month ago saying i never returned and no found in warehouse. I also called bunch of times. They said "it takes time to get adjusted in the system" more than a 6 month later. They said i never returned so i pay everything. Too bad i only have email confirmation with tracking number from ups. Who would thought they will scam me after more than a half year. Tracking number doesnt exist anymore and im stuck with the bills for returned phone. I only have few payments left and im leaving tmobile for good. I regret switching over to tmobile in the first place. This all 3 fraud happened straight during about 3-4years of being tmobile customer. Never ever get tmobile. Life lesson learned. Keep your receipt forever and make sure receipt doesnt get ruined ot erased. Usually even ups tell you to keep it for at least 3 month just incase. Who would thought they will do this after several months past.