unable to add credit/debit card or set up auto pay

Same issue. Prepaid user for years (the old "Walmart plan"). I went to the retail store, and they also couldn't do anything. They asked for cash, which I didn't have. They told me to call the prepaid service number, which I did. They were also useless. My service was canceled due to non-payment. Since my bill is only $30 I found a workaround by buying a $30 prepaid refill card online through Walmart that described itself as "email delivery". However, you're able to put your phone number into a field in the cart on Walmart's site, so they applied the payment directly to my account. After making the payment through Walmart I was notified that my account was re-enabled within 10 minutes. This is pretty pathetic. Multiple T-Mobile support entities (retail store, phone support, and prepaid phone support) couldn’t apply a payment to my account, yet another company (Walmart) could.