T-Mobile provides several ways to add credit directly to your account:

Buying T-Mobile phone credit online is direct and can be done through official T-Mobile channels or authorized third-party retailers. Digital payments are often free and can help you avoid a $5 Assisted Support charge that applies to in-store or over-the-phone refills. Official T-Mobile Refill Options

Choose a one-time payment or set up using a bank-issued credit/debit card.