I dont want a cover with a R500 voucher. False adverti*****t!

I upgraded my contract on the 1st August 2018, after which I really didn't have a choice from R249 to R799 a month as firstly MTN don't stock HTC anymore and secondly Samsung S9+ is the closest I could come to HTC. I was excited to see that there is a voucher for R500 on the box. The minute I tried to claim the voucher the store at Soneike said no I had to go a Samsung store. So I drove all the way to Samsung in TygerValley just for them to tell me (rudely) NO, they don't do it anymore, they only helped out MTN before and I have to do it at MTN. I then went to the MTN store in TygerValley and they said I can choose between one cover. No real choice there. I don't want a COVER. I want accessories as advertised. I then went back to MTN Soneike and there the manager said NO I can only have a cover and they only have two covers and they need to order more. I DONT WANT A COVER. I want a fast charger as described in T&C here http://images.samsung.com/is/content/samsung/p5/za/offer/galaxys9-preorder/APS-Voucher-Campaign.pdfI have been with MTN for more than 15 years but they really starting to make me mad with their expensive data and expensive deals.