I just tried to book this and failed miserably...please tell me where I've gone wrong.

1) I understand you can't book this online.
2) I phone up (00800 228 21000->#1) and the lady had never heard of the deal - I quoted word for word "Marriott & JW Marriott Hotels: Treat Yourself to A Weekend Escape and A Free Second Night" - and read half the page out to her.
3) After 10 minutes I gave up...

- Does each hotel have limited capacity of this deal (or is it like the IC BOGO)?
- What should I be asking for?
- Is it valid on all room types?
- Am I calling the right people?

Help..
(I'm Gold)