In this case, it is not reasonable and legal for the bank to charge interest that is more than three times the principal.

First of all, according to universal legal principles, fees should be fair and reasonable and must not violate the principle of good faith. Banks clearly violate this principle by charging interest that is more than three times the principal. According to the basic principles of contract law, both parties to a contract should reach an agreement on the basis of equality and voluntariness, and this interest charge obviously does not meet this basic requirement.

Secondly, banks, as financial institutions, should bear certain responsibilities when providing credit card services. However, raising interest charges to three times the principal is clearly beyond what is reasonable. This move not only seriously damages the interests of credit card holders, but also violates the bank's obligation to provide fair and reasonable fees.

In short, it is unreasonable and legal for banks to charge interest that is more than three times the principal. Such charges not only violate contract law and the basic principles of financial institution responsibility, but also harm the rights and interests of credit card holders. In this case, the cardholder has the right to safeguard his or her legitimate rights and interests and can resolve the problem by communicating with the bank, seeking legal assistance, etc.

Extended information:

Credit card overdue means that the cardholder fails to repay the credit card debt in accordance with the repayment period and amount agreed in the contract. Overdue payment will result in high late fees and interest, which will seriously affect an individual's personal credit record. Banks usually take certain collection measures after overdue payments, such as phone reminders, letter collections, etc. If the overdue period is too long, the bank may take legal measures to implement recovery measures, including submitting the overdue person's personal information to credit reporting agencies or taking litigation to recover the debt.

However, banks also have certain restrictions on fees. According to relevant laws and regulations in my country, banks must be fair and reasonable when charging fees, and must not harm the legitimate rights and interests of consumers. This means that banks should abide by the principles of market fairness and competition when setting rates and charging standards to ensure that charges do not exceed a reasonable range. For credit card overdue interest exceeding three times the principal, it is obviously beyond the scope of reasonable charges and infringes upon the rights and interests of consumers.

Therefore, when individuals face overdue credit cards, they should pay attention to reasonable management of debts, abide by the repayment time and amount stipulated in the contract, and prevent high late payment fees and interest. At the same time, if the interest charged by the bank exceeds a reasonable range, individuals can safeguard their legitimate rights and interests by negotiating with the bank and seeking legal assistance.