Bad Service@Samsung

I bought a cellphone Galaxy Note 20 and claimed for the R4000 e-voucher on the 12 Sep 2020 and claimed the R1000 for UV Sterilizer on the 24 Sep 2020, on the 26 Sep 2020 i received 2 sms' to with the voucher code to redeem the R4000 and R1000 but the voucher number was the same for both items then i redeemed the R1000 UV Sterilizer first and i received it today, then i tried to redeem the second item for R4000 then i got a message that the voucher number it's invalid. I called the customer care line on the 26 Sep to send me the correct voucher for R4000 but I'm not winning, i waste my airtime everyday phoning them to fix this and they keep on saying they will call me back and no one phoned me. I'm not happy at all with their service.