My boyfriend''''''''s ex girlfriend ran up his credit card bills. Last night, he received a claim for arbitration from MNBA Bank handled by CACH, LLC. They want almost $6,000 on an initial debt of $3392.43. He is to respond within 30 days.
What do we do?

Optional Information:
Seymour, Missouri

Already Tried:
Just got it last night. Have a phone call in to a lawyer but have not heard back from him. So far have been scanning the internet for answers.