I wonder if that is a person at your local TC branch or at head office? What I found sad with TC is that every member of staff in my local branch, without exception, was wonderful. It was the elusive ones out of the public eye who seemed to cause the problems and then do a Houdini when you tried to get a hold of them! Keep us posted. The do have to resolve this for you. I don't suppose they told you there was a substantially reduced outstanding balance when you went to pay yesterday. I just find it incredible that you booked it and were invoiced for that accommodation, yet not only did they not tell you that it had been cancelled (for goodness knows what reason), but nobody actually came back to advise you of a proportionate rebate.
I just remembered I had the opposite problem last year. Booked the Hilton at Machester airport (we live in Scotlant) then changed my mind and decided to go with the Raddison. They cancelled the HIlton, charged me a £7.50 cancellation fee and I booked the Raddison myself as they didn't have it on their system. When I got my tix etc, they gave me a confirmation for the Hilton, receipted as fully paid?!?!?!?