Miscommunication about the 20% discount FNB card

I recently got an email form FNB informing me that if I purchase any goods on groupon I will get a 20% discount on my purchases if I use my FNB credit card. I even called groupon to make an enquirey as to how this will be app**** because after attempting to purchase the goods, the discount hadn't been app**** but I was assured by a groupon consultant that after the transaction went through, I would get my reimbur*****t. However after ordering and paying for my goods and seeing that I didn't get any refunds (20% discount), I called groupon again only to be answered by another consultant who now infomred that oh no the discount will not apply as the goods I purchased were on sale and that the TCs specify that it only applies on fully priced goods. Different story altogether, why was I not told about this when I called initially and yet also I didn't see any of the TC's on the email I received from FNB in the first place. I have been ******* into purchasing goods by Groupon and am so disappointed.