Personal financial information is accessed or used without the account holder's consent.
Knowing someone's bank details — because they were shared for a previous purpose or simply discoverable — is not permission to use them. Access and authorisation are not the same thing. Using another person's financial details without explicit consent is both a civil and criminal matter, regardless of the intent to repay. The promise to repay does not retroactively authorise the use.
After you respond, they may push back with these arguments. Members get the full rebuttal for each.