Callsign Confusion
Recently whilst receiving a FIS from XXX, a regional airport, I realised my abbreviated callsign was identical to a training flight on the ground at XXX, but the controller had not realised this. The conflict was obvious to myself, and I tried to alert the controller to the situation by replying to messages directed to myself using my full callsign. Unfortunately the controller didn't take the hint, and as I was about the leave the frequency shortly I didn't worry too much.
My question is "Is there an approved phrase that I as a Pilot can use to alert the controller to the situation?"