Debonairs Live Chat horrible!

Tried to use my R 50.00 birthday coupon Debonairs sent me, picked my stuff & went to checkout. Put in my voucher code in (BDAY50), the total to pay was shown as R 149.90 but when the deduction SMS came through it said R 199.90. Obviously shocked I immediately went to the Live Chat option on the Debonairs App & waited for an agent. The agent was slow to respond & completely unhelpful. When I told the agent that the App defaulted all they said was that the voucher wasn't redeemed when I know I did the right thing. I saw the total before I clicked pay. The customer service on the Live Chat option is horrible. Ruined my birthday today.