Changing flight booked through travel agent

We have a flight booked for our upcoming trip to Barcelona. Booked through travel agent. American Airlines changed the time of our flight to Dallas from KC putting us there about 1:35 before our flight to Barcelona. It was originally scheduled about two hours earlier. I attempted to have travel agent change it to an earlier flight that is available but he said we would have to cancel all flights and rebook. Any of you had this issue with American and been able to get it changed without travel agent?