Poor customer service

I received an email on my birthday to receive R100 discount on a R500 purchase . I followed the mail and tried to buy stuff on line with no luck, telephoned the help line who also couldn't assist and was then told to go into the store to buy my stuff. Went that afternoon to Norwood Mall, chose my required products with the printed email only to be shunted around and then told I do not have the correct code. Why send out an offer with incorrect info. Really makes me not want to use your store again. I didnt request the gift--you offered it and then make it impossible to use WHY? what is the point of that???? Since then I have emailed 3 times asking for an explanation and have been ignored. What sort of customer service is that. Disgusting behaviour???