Activate a card over the phone by calling the number printed on the attached sticker and following the prompts, according to CreditCards.com. If the sticker is not on the card, call the customer service number for activation.
In order to activate a card by phone, CreditCards.com indicates it is sometimes necessary to call from the home phone number. The verification process sometimes takes longer for those who call from an office or a cell phone, as the agent checks his caller ID for the phone against the number on the original application. Cardholders who prefer skipping verification by phone often have the option of verifying the card through an online banking account.