I am unable to use my normal credit card (Mastercard) to refill my account. I've tried from three different devices using three different browsers, but it always says the transaction failed. I checked with the issuing bank, and nothing is wrong. I then called T-Mobile, and the customer service agent was unable to get it to work. The agent (0440) described the error message as "vague."
After talking to two other agents we were able to make the payment by "holding the charge," whatever that means. I've since tried the card at other stores, and it works fine, so it seems like something is funky one T-Mobile's end. I tried using a Canadian credit card (VISA), and it works fine, but I'd rather not have to do this later.
What is going wrong, and how can this be fixed?