KFC pathetic service

Good day, I would like to complain about one of your branches. I ordered food via whatsapp for collect at your N1 city branch in cape town. Upon arrival cashier rung up the order and I advised that I had vouchers I wanted to use. When they tried to enter the codes apparently it didn't work. They then called the supervisor named Felicity and all she told me is the system says failed I have to pay cash. I cannot understand how a voucher which was awarded while playing your game failing on your system becomes my problem. I asked her what's the solution because it's not my issue I came here to specifically redeem the voucher and she told me she can't do anything since she doesn't know if the voucher had been used. I again asked so what's the solution she told me she can call I'm not sure who but it'll take forever for them to answer and assist. Please make me understand what type of service this is. Also when we came to the store they didn't even prepare our meal eventhough we ordered on whatsapp for collect and pay and were told we must wait 7 minutes for the chicken. I honestly do not understand what the point of us ordering before hand is. The lady just told us if we don't pay online they don't prepare it incase we don't show up. Please advise what type of convenience and service you are offering because I don't see how us as customers are being assisted. We are just treated as inconveniences.