Has this happened to you?

My daughter and I did the "free trade in" for phones a while back. One was actually free, and the other was charged the monthly plan amount. It took THREE MONTHS to correct this - I don't know how many people I talked to, but I had to reach someone who spoke English as a first language in order to get this squared away, despite promises and guarantees that it would be solved. Cue next daughter to do the free trade in - we are in mid-problem right now. Yet again, I'm paying the monthly installment for a "free" phone. The first call netted NOTHING - no credit, no plan change, just a waste of time. The second call netted the credit for two months of charges, but the installment charge still shows on my plan. I told them that if I was charged yet again for the installment plan, I would QUIT T-Mobile. The agent GUARANTEED that she escalated the issue to her supervisor and that it would be resolved in one to two cycles. I told her that was unacceptable - if it wasn't fixed by the next bill, I'M DONE. We'll see what happens, but I'm not confident that I will be with T-Mobile by this time next month. I don't trust T-Mobile, and they have done NOTHING to instill confidence in me regarding their customer service.