Is a note from someone who owes me money enough to prove my case in court?

My ex bf owes me $1200. I loaned him money for his rent, cell phone, truck , and random atm withdrawals. Over text messages we agreed that he owed me $1800. He paid back $600 through paypal. in one of the transactions he wrote a note in the comments section stating the balance he owed me. Recently he claims he is paid in full and doesn't owe me anything else. Do I have enough evidence to sue him for the rest of my money?