T-Mobile USA review: Customer service, online account access, access to view bill once moved to a new carrier.

We have been a Sprint/T-Mobile customer for 20+ years. Our bill was getting high and our phones were old. We went into a T-Mobile store to talk to an associate about various plan options and phone upgrades. They told us, that they could not pull up our account in the store, and they no longer provide that service, we would need to go online to look at plan options and phone upgrade options. WHAT? Where is the customer service. Just prior to us going in our son had broken his phone and went into the store to buy a new phone and paid cash. They talked him in to adding a line to the account, saying it would be no cost until we started to use it. 1. he is not an authorized user, 2. the next month we got a $10 charge on our bill. With no support from a T-Mobile representative we talked to another carrier and decided to move all 5 lines. Now I attempted to log on to my T-Mobile account, to view and pay my final bill and confirm all lines have been moved and that random line is cancelled and apparently because we moved all our lines I ca longer log into my T-Mobile account to see my bill. All these companies want customers to go paperless and do everything online, so I should be able to go in and see my current bill and even access old bills. I called, and the rep said - yup you cannot access once you move. And said I can pay as a quest but it will not tell me the balance due. How ridiculous! I should be able to view my final bill. I was told I can go into a store and show them my drivers license and they can then access the account. REALLY - why did the sales person tell me they couldn't when we were looking at plan options and cell phone upgrades. What horrible customer service. T-Mobile corporate leaders need to be made aware. You have lost a loyal customer, who has been with you for 20+ years. I am sure I will not get any type of response to this but honestly - at least grandfather access to an account for 30 days after service is transitioned to a new carrier, so the customer can view their final bill and make payment. How is making it so difficult make any sense.