It is not illegal to pay off a credit card on your behalf. Repaying a credit card on behalf of others is a civil act and is not illegal. You will not be sentenced, and you do not need to bear the responsibility for civil compensation or administrative penalties. Only those who commit credit card fraud constitute a crime and will be sentenced by the court. The Zhongxin Repayment Platform only helps others to repay money on their behalf to relieve financial pressure, and does not constitute a crime.