Neither do I.

EDIT: Just realised you are not the same person as the OP - bofc

bofc:

Are these the same T&C you had.

Where do they claim it stated that purchases had to be within the promotional period?

- Is it possible that this agent didn't really know what they were talking about and that everything is actually fine?

If you have satisfied the conditions of the offer, I'd keep approaching them on the basis of asking for confirmation that you have satisfied the conditions of the offer. However, given that you have been given this answer, I would be asking now for this confirmation, rather than effectively letting what you have been told stand.