Consumers continue to rely on credit cards as a payment mechanism but they are gradually whittling away at the balances on their card accounts that are accruing interest. And the number of card accounts is in decline.According to the latest Reserve Bank payment data, the total value of transactions on credit and charge cards in April was A$27.5 billion. That is in line with the previous month and 2.7 per cent higher than the same period last year.The value of balances accruing interest in April was $31.5 billion - down from $31.6 billion in March and down 2.8 per cent on the same period last year.Just looking at personal cards, the value of balances accruing interest fell 4.9 per cent to $29.5 billion over the 12 months to April. That is $2022 per personal card account.The number of card accounts is down 2.9 per cent to 15.8 million over the past 12 months. In terms of personal accounts, the drop is 3.1 per cent to 14.6 million.