How to set the PIN on your Mastercard. Credit Cards: 844.334.3874 (the number on the back of the card) Option 7 and follow the prompts Debit Cards: 800.472.3272 (number on the back of the card) or 800.922.3808 (card self-service) Option 1 for activation and follow prompts Have more questions? Submit a request 0 Comments Article is closed for comments. Related articles Why is my 3Rivers debit or credit card being declined? Mastercard debit card or Mastercard Credit Card was lost or stolen. Who should I call? Vacation Debit Card Blocked States and Countries How does 3Rivers help protect me from fraud?