The TA booked your flight. Now you want him to cancel your flight and process a refund. He doesn't work for free. $225 seems high to me. I wouldn't have booked with that TA. You must have had a reason for not booking directly with the airline.

The TA doesn't want to deal with customers who are wasting their time. I agree with the pp. See if all, or most, of the $225, can be used as a credit for a future booking. Make sure whatever you book isn't costing $300 more then if you booked direct.