Some downloads and apps require immediate card payment while some apps allow T-Mobile billing.
Tmobile can verify your ID and maybe fix your problem on Facebook or twitter or over the phone.
I had the same issue. I spent more than 1 hour talking to 2 TMO customer care reps and one Google rep. At the end, T-Mobile technical support rep confirmed that I can't use carrier billing because I have free Netflix+Family Allowance. That's a shame T-mobile.
I had the same issue but I spent more than 3 days talking to three T-Mobile reps, 2 Google department supervisors .. one of which was from Google Business , 1 Google security administrator, and 2 of the Google Play developers not to mention LG tech support with no luck at a finding a solution from either of the people who have been working with me on this ...
FINALLY ... as of 4:50 am Dec10-2017 ... with the help of this topic, i am able to make the necessary changes needed to fix the problems