free phone scam?

Have been a t-mobile customer for years. Phones stopped working. We were not told, that they were working on towers. Told us we could get new phones for free, with trade in. She slipped paper work in bag. Phones price $1600. Next day we insisted they take phones back and return ours.  They refused, and said there would be 150. restocking charge. They said if we come in each mo., would credit. Store was 50 mile trip. On 1 store visit, was basically called a liar. Was told I signed printed paperwork. Not true. Called t-mobile. Was told they would credit some, but balance would be 650. Agreed to pay the 650. On next bill, was billed 1000.  I far as I'm concerned, that voids deal. I am done.  This has been going on for 10 mos. Everyone should get together and do class action law suit.