Credit Card Customer Service Call: 866-820-3947Credit Card Activation Call: 800-527-7728Lost or Stolen Credit Card Call: 866-820-3947Within the United States24 hours a day, 7 days a week Call: 00 + 1 + 314-542-7111Call collect from anywhere globallyCredit Card Payment Mailing AddressMastercard®P.O. Box 71050Charlotte, NC 28272-1050