By 'pay', do you mean Debit: Credit Card account and Credit: Bank account or payment to the credit card company?
Are you amortizing from the time the credit card company was paid? (Wouldn't hurt though if the expense and the payment to the credit card company were recorded in the same month, especially if amortizing if by periods too)
From the accounting perspective though, we would normally amortize from the date of recording the expense not when paid. Just curious.