I have a C award booked for 120k for LAX-TPE / SIN - JNB - LAX (via LHR).

On Thanksgiving day I wanted to make a change to get on an OZ flat bed. The agent had difficulty and said my ticket wad booked in error and flagged it as a round the world trip. Now when I call them they transfer me to the *A desk. They won't make any changes because there is now documentation for my PNR stating that I can't do this.

All I want to do is to change the dates . I am willing to drop the LHR crossing and go back through the Pacific to LAX. But some Continental agent is refusing to hear me out. Should I keep it or try to call them again.
Any advice is greatly appreciated.