You can change how you're paying for GitHub at any time.

  1. In the upper-right corner of any page, click your profile photo, then click Settings. Settings icon in the user bar
  2. In your user settings sidebar, click Billing. Billing settings

  3. Click Update payment method. Update payment method button

  4. At the top, choose to either pay with a credit card or PayPal. Switch Billing payment methods

Further reading