Uber Eats complaint: Uber Eat refused to honor an offer code after checkout

I have five 40% OFF promo code in my account. I placed an order this afternoon which includes a Buy One Get one Free item. Before the checkout, the app clearly showed that both offers could be applied. (The restaurant lists an item which has twice of the portion as the BOGOF item but it has the same price.) After the meal is delivered, I found that the 40% OFF offer was not removed. I called Uber and they explained that there is a condition of the offer which says it cannot be combined with other offer. So I went back and double checked the fine text and it does mention this. But the problem is, why their APP allows both offers to be applied before I check out, but only remove the offer after I have paid? This is an action beyond dishonest and disgusting. Besides, when I tried to resolve the issue with their customer service, I was hung off by two different people and they refuse to take my call anymore. Just as its employee, Uber Eat takes no accountability for its dishonest action and think it can do whatever to its customers.

The attched picture below shows that Uber APP allows both offers to be applied before checkout.