Anyone else's bill go up double without explanation a few months ago???

I have tried to get this resolved multiple times now. 3 one hour plus online chats, one hour and half long visit to the store I got my plan from, and lastly an hour long conversation with a "Manager" who promised me that my bill "would return the previous charge amount by next cycle. You will receive an email in 9-10 days with confirmation as well." I asked for their contact info and they wouldn't give it. Needless to say I didn't get the confirmation email and my card was just charged double what my bill should be AGAIN! Long story short, I was promised a "deal" in store and my monthly charge was $120-ish for 8 months. Tmobile issued that small upcharge mid year this year and something in the system automatically added a "service charge" to my account. I can't anyone competent to see it from my side and assist me.