Can someone please tell me when I am holding a full fare Y class on a paper ticket then I call and change it to another day CO says that I have to go to a CTO or ATO and have it "reissued"...

This prevents me from geeting in the queue to be upgraded until I make a special trip to the CTO. Is this true what they are telling me or can I force them to show the ticket as issued somehow since I havea ticket number and paid full fare?

THANKS!!