As a T-Mobile One Choice plan user for two years, I have to say the customer service is the least satisfying. It is not just one time. It happens a couple of time with repeated mistakes.
For example, a few months ago, I simply wanted to merge two existing lines into my family plan and the customer representative over the phone told me to go the nearest retail, so I did. But it turns out that when I arrived at the store, they told me that I need to call the hotline since they can't do anything about it. So I called and this time, the representative handled the issue was able to solve it. It was such a waste time to go to the retail while that not-very-well-trained representative was claiming that it was the only option for me to do.
Few months passed. Now I have to remove a line from my plan and get a new number with new sim card for it. It was also over the phone. Instead of doing so, the representative added an extra line, so it ended up billing me for that. I contacted the customer service and told him how much I was disappointed. So he told me he is gonna adjust the credit for me and to wait for another day or two to reflect in my account. Two weeks passed and nothing happens there.
Now for the upcoming billing cycle, they are charging me as much as TWICE the amount. and God knows why. So here I am waiting for another so-called representative's response and writing down my fabulous experience with T-Mobile here. Trust me. After I've made full amount of current equipment installment, I will never be using your service again. Such a terrible expereince.. Thanks T-Mobile!
P.S. you are the busiest customer service yet nothing is solved properly without following up.