Nandos not taking ownership

I am a regular customer at nandos louis trichardt CBD as I work around the area I always have my lunch at nandos,since the special of R49.00 quarter chicken and side started it became evident that il be eating there almost every day, until Thursday the 17th February where I ordered online as usual and I sent my worker to go pay and pick up the order,yo my surprise the receipt he camebck with showed that I the bill was R59.00 instead of R49.00 so because I have subordinates who buys from there I then called the manager to tell her that on the app it says R49.00 and I have been buying using the app and I have paid R49.00 you can check my app history even on the 14 February I bought 2 of the same meals and I paid R100 from the same store,however the lady told me that orders made on the app are charged extra..I even said I have 4 more people who buys using the app I can provide proof of what am talking about,I only know that nandos charges extra of its delivery..however the lady insisted that she was right in charging the price I should contact customer care but they won't help me because they will direct the call back to her and she will give me the same answer..indeed I called customer care and that what exactly happened she called me back and told me that the answer its still the same,I called customer care again whereby I spoke to njabulo who said that the supervisor will be in touch,since the 17th the supervisor never got back to me,I then sent a DM on Twitter explaining my story,the same manager the called me and told me head office will answer me she doesn't get involved then she hanged up,I DM nandos again and they said they referred my query,still now am waiting for response from nandos since Thursday..this really frustrated me as it is Taking my energy and my time.i do not think nandos its a place you will wanna dine in.