If there was a way to rate it 0, I would. I was tagging along with my sister-in-law who wanted to get a new phone. The 1st obstacle is that you now have to pay full price for phones, but she knew that going in.
The problem was the store clerk could not answer the most basic of questions. "It's there a trade in value on my old phone" answer "maybe", "can I switch the SIM card from my old phone to the new one and get a new SIM card for the old phone and still use the old phone" Answer "possibly"
Honestly every question was answered "maybe" or "possibly" we never got a straight answer from her. It was like T-Mobile pulled her off the street and put her in front of the register.
When visiting the t-mobile store you expect them to know something about your account and your options, I'd expect this from Wal-Mart where they have different carriers being represented, but the clerk's at Wal-Mart were much better when we added a phone a couple of months ago.
T-Mobile may have better plan pricing but there is no way I'd ever switch after seeing the lack customer service the provide.