MTN: false sales/promotions

Good day I am highly upset and disappointed in the service on the 2nd on June 2018 I upgraded my contract to the samsung note 8 I was then told that I will get a voucher with the phone for R300 off any note 8 covers or Samsung mobile for the note 8 products, I then went ahead with the deal, once I got the phone I then walked out of the shop and walked into samsung canal walk where I was then told that I can not use the covers at a samsung store but only at mtn, i then walked over to a different mtn in canal walk and there I was told I could not use it for covers but only for the samsung deX and the samsung wireless charger and that the voucher is only for SAMSUNG BRANDED PRODUCTS for the note 8 and I then asked when the voucher is valid until and was told until the 30 June 2018 I then left it and got some cash because I wanted the Samsung deX on the 29 of June 2018 I walked into mtn and when I wanted to purchase the samsung deX I was told the the voucher has expired on the 31 may 2018, I would like to thank you for the embarrassment you've cause me and selling me something that was invalid I will no longer recommend your services as I have been doing that and I hope that future you will not sell invalid promotions..