Legal analysis: it is not illegal. 1. As long as the money is owed, the bank may sue, which is up to the bank to decide; 2. If the amount owed reaches more than 1, yuan and is not returned for more than 3 months after being collected twice by the issuing bank, it shall be deemed as "malicious overdraft" in criminal law and suspected of credit card fraud; 3. If the amount of malicious overdraft is relatively large, and all overdraft interest has been paid before the public security organ files a case, and the circumstances are obviously minor, criminal responsibility may not be investigated according to law

Legal basis: Article 673 of the Civil Code of the People's Republic of China

If the borrower fails to use the loan according to the agreed purpose of borrowing, the lender may stop issuing the loan, recover the loan in advance or terminate the contract.

article 674 the borrower shall pay the interest within the agreed time limit. If the time limit for paying interest is not stipulated or clearly stipulated, and it cannot be determined according to the provisions of Article 51 of this Law, if the loan period is less than one year, it shall be paid together with the loan; If the loan period is more than one year, it shall be paid at the end of each year, and if the remaining period is less than one year, it shall be paid together with the loan.

article 676 if the borrower fails to repay the loan within the agreed time limit, it shall pay the overdue interest in accordance with the agreement or the relevant provisions of the state.