T-Mobile USA review: Wireless service

I have been a customer with T-Mobile for about 10 years. I added a line for my son back in March after shopping around for other service providers, I decided to go with the one I knew and thought that I could trust. My first bill was $171.00 with the new line which was different than what I was told prior to accepting the new plan. I spoke with a supervisor named Jellyane B back in June and she told me that my bill was fixed and I would be paying between $141 and $143 per month for my service. Every month since I have had to call in to request that the adjustment be made since I was still being billed $171.00. There were months when I had to make multiple calls to T-Mobile which quickly became frustrating. I would be asked to go over the original issue repeatedly and eventually, there would be a credit added to bring my bill back to the 140 something I was promised. Last month, I was told that someone would call me back to discuss the billing issue and fix my account once and for all. I never received a call from T-Mobile and like clockwork, I received a text telling me my bill was again $171.00. After speaking with 3 reps, I was transferred to a supervisor named Evan H (ID#0523-Springfield). Evan advised me that they would no longer be honoring the billing agreement set in place by another supervisor. He was able to see where the agreement was reached but stated that the adjustment would no longer be made. Evan offered to cancel my service for me and advised he could not provide me the number for the corporate office. This is not fair to me as the consumer especially since this was an agreement that was made with me and at this point, I am having to switch service and being told that I cannot take a phone number that I have had for 10 years. I have never had a member of management speak to me in this manner and verbally admit that the company is now without notice backing out of an arrangement that they committed to. Over the last 5 or so months I have been paying between $141 and $143 because while shopping around, I originally told the representative what I was able to pay so I did not expect that someone would reverse this agreement with no warning. The customer service has definitely suffered in the last few years since the company became so big but I have been a customer from the beginning and I do not believe that the manner in which Evan spoke to or treated me was in any way professional. Its not wrong for me not to want to have my bill be what I was promised or for me to be frustrated about spending so much time on the phone on a month-to-month basis to have it fixed.