abuse of the poor

I regularly order from Ubereats to get food, as I have a disability and cannot always leave the house. I am on a very tight budget and have to shop around for the deals. UberEats Market advertise 50% off on Tuesday for fresh produce, and so I did most of my shopping from that section. Low and behold, after I paid I discovered not even one of the discounts went off and I paid full price on all items, doubling my total bill. I am in urgent need of this being rectified so that the amount I was over charged is returned to me at once or I will not be able to survive the month. Please help!