Problems with linking my internet phone number to my t-mobile ID

If it is any consolation, I am facing the same problem -- unfortunately, I don’t have a solution, but I certainly wish someone would post here with an answer.

It took me three full weeks, including four phone calls to customer service, to even have the system recognize my email. I finally was able to create a T-Mobile ID. When attempting to log-in, I enter my email and password. A verification code is sent to my email. When I enter that code instead of going straight to my account, I get a screen asking to link my phone number to my T-Mobile account. "Enter the phone number [in the box] below to link your account, and we'll send a confirmation code for verification." When I enter my (non-T-Mobile/Sprint) cellphone number, it is not recognized ("Please verify your 10-digit T-Mobile phone number is correct.") -- of course it is not recognized; it is not a T-Mobile phone number.

When I enter the internet line number that is listed on the gateway (modem), what happens? I get the same useless error message that I was getting for three weeks: "We're sorry, we don't recognize this email. Please provide the email you used when purchasing your T-Mobile service or contact Care by dialing..."

All of the customer service people are friendly and professional, but no one can solve the problem. I cannot believe that setting up a customer account is so difficult.