Please verify your 10 digit T-Mobile phone number is correct

I still cannot get into the tmobile website to manage my account.

First, the site accepts my email address and password. Next, the site states, "The application you are trying to access requires a phone number. Please add a phone number to proceed."  Then, the site repeatedly states, "Please verify your 10 digit T-Mobile phone number is correct."

The phone number is active. It can place and receive calls. However, the site will not recognize the number.

I ported this number to Tmobile ~6 weeks ago. I have tried numerous calls to customer support, but the representatives are unable to help or they repeatedly say to wait 72 hours.

It is unfortunate that I may have to switch providers just because tmobile makes it inconvenient to pay my bill.