OP was asking about cash upgrades and the disparity in info from CX (the operating carrier) and BA (who sold the ticket).

It could be point-of-sale, systems issues, etc. Is this a CX flight number or a BA codeshare ?

Depending on the fare paid, and the restrictions, it could vary from expensive to not possible. Or it may have fallen into the 'too difficult' category. Do you know the fare type and rules ?

Check on the CX board to see if they offer MMB, OLCI or airport upgrade offers similar to what BA do.