Advertise promo, then dont refund when promo doesn't apply

whilst browsing kauai on your app, i see a special that says get a free C smoothie on orders over R100... my order was going to be R89, but i usually order a smoothie as well anyway, so good deal for me. I added another item (protein bar) to my order to bring the total above R100, and selected the C smoothie. Right away I saw the amount for the smoothei reduced to zero in my cart. At checkout the R50 smoothie fee was back again. I figured tech issue, and processed sale, only to see that full amount had been charged. I wasn't concerned becuase a R50 refund is not hard to process. I sent through my issue with the order. No response. I sent again the following day. No response. After the 3rd time, I received this,

Hi Mike,

We understand this has been frustrating and are sorry to hear this has been such a poor experience for you. Unfortunately, we are not in a position to offer a price adjustment for this order. We appreciate you taking the time to let us know your concerns, and want you to know that we are constantly aiming to improve our services to you. Thank you for your understanding. Sent by Rehman Zahoor on Monday, January 11, 2021 at 7:23:47 PM

Well, for R50 they have lost a daily uber eats user. short sighted indeed. I wont use their taxi service either now.