Poor service

I was in KFC Sky City on the 12th March I bought the All in one Mega meal at the Kiosk for R169. 90 and realized after that they were actually running a special and selling same meal for R149. 90, I then approached the cashier to help me cancel the order I made so I can make the one at the discounted rate and she told me that there is no way of helping with that as my transaction was made at the Kiosk so my question is whose Kiosk is that if the staff at KFC can not help me as though it is operated by another company other than them. I lodges a complain on the KFC app on the same day they said they required more information and gave me a number I can call, I called them the following day the automated machine said they were all busy I must leave a message which I did but they still haven't called me instead I get a message today that my case has been closed. That is poor service at its best, I a disappointment in KFC!