Can I charge a former tenant’s credit card?

I have a question about charging a former tenant’s credit card. I have a former tenant with a fairly low credit score who was renting my furnished rental. I was nervous about his bad credit, so I wrote into his lease agreement that I will charge his rent automatically every month to his credit card. The utilities were also in my name (because it’s a furnished rental) but he eventually decided to stop paying his utilities. He eventually stopped paying his rent, and he wrote me in an email that I’d “better not” charge his card for the last month of rent he owed me. I haven’t charged his card yet. Do you know whether I have the right to charge him? He signed a contract giving me permission to do so.