Call centre confusion

Hi, I moved house and as a result my mail has still been going to the old address. Truworths issued me with a voucher *** which was valid until Sunday 7th April. Unfortunately I only received the letter late and was unable to use it. While at Cresta shopping mall this morning - at 8:55am I called the customer centre on ********** and spoke to a consultant explaining my predicament and asking if they could by any chance extend the validity of the voucher by 2 days ie I would use it this morning at the mall. She asked me to take it to the Truworths store and they would handle it. So I went to the store, chose an item and went to the till. The lady had to call head office to confirm what they said. The supervisor (I have her name) was rude and unhelpful, even shouting at the teller and going as far as to say that the telephone lines were down and I could not have phoned them! For the record, I have a screengrab to prove that I made the call and that it was around 3 mins duration. They also had no idea who I spoke to. When I made the call earlier, the lady had put the phone down just as I asked who I was speaking to. Ironically - when we checked at the store, my address had actually been changed to the new one, so the voucher should have been sent there. Also, surely your call centre people should be able to give a clear answer when we call with queries. With a queue behind me, I made the purchase as I could not use the voucher. However, in light of the above I believe it would surely be good practice to extend its validity, albeit for a few days.