I'm a long-time T-Mobile Customer and I don't mind letting the sales folks make a living. The phones and service is good in our area and less expensive overall than any other provider. If I want help or information, maybe a new phone they've been more than willing to assist or give me a phone for free, or maybe to test drive, which I've done for a week or two. If you know someone in the store and they know you’re a long time customer, I think any provider would enjoy being helpful and would give their sales staff the latitude to keep you satisfied.
