I'm not defending T-Mobile, but you just outlined why they are making this change. People are abusing the system by disputing charges valid or otherwise. Banks require a higher burden of proof to return funds, where most credit cards will immediately revoke the money from the merchant if you file a dispute and it might cost the merchant more to fight it than to just let it go.

Again not defending T-Mobile, they do have a bad track record with data privacy and could have handled this in a different way. For example, being able to use a credit card for auto pay could be a loyalty bonus for long term customers or after completing a certain number of on time payments. Another option that could be good for T-Mobile and customers would be to partner with a Credit Card provider to offer a card with cash back perks. T-Mobile could work with the provider to tweak the dispute terms more in their favor and the customer could get a cash rewards card and wireless service with a single credit check.