Is this a violation to privacy?

There is a guy who works with me who used to be my friend. Two years ago he asked me for help to buy a new refrigerator because he had bad credit. I told his we could buy on using my Sears credit card. He agreed to pay me in three months. Two years has passed and he hasn't paid the full debt yet. The fridge was $1,129.00 and he has paid me only $900.00. with interests the debt raised to $1,444.00, so he still owes me $544.00. For two months he has not given me any payment and always finds a way to hide from me. I plan to go and talk to him directly about that debt and record the conversation without his consent, so I can take that to court as evidence of the debt. I need to know if it is legal to do so.