Hey Corey! It depends on how the access to bill purchases to your account was turned off. You can test by going to the Play Store > Settings > Account > Payment Methods. If you're able to select the "Bill my T-Mobile..." option, awesome! If not, then it may have been disabled on the T-Mobile account side rather than in your device.
If it was disabled through Family Allowances, and you're the Primary Account Holder, you can manage Family Allowance settings through MyT-Mobile or the T-Mobile app. If the access was removed with Content Blocking, you can manage that through the website as well! Were you able to bill purchases to your T-Mobile account before? Do you know how it was disabled?
Manage your T-Mobile account