I have a client who signed a contract for $780 for website design. He paid $400 on his credit card and promised to send a check for the balance. While I do have emails from the client acknowledging he owes the money and the service was performed to his satisfaction, all subsequent emails and calls to him regarding collecting the balance get ignored. I do have a signed contract that says he agrees to pay the entire amount within 30 days, but does not specifically say we can charge his caredit card. Can I charge his credit card again to collect the balance?