Incorrect refund

Last week, I saw Uber eats having a Buy 1, Get 1 free deal at KFC, So I grabbed the offer & bought 5 double stack burger, which my my maths is 10. (5x2). I only received 5 burgers. I contacted Uber eats and realizing their mistake, they said they would refund me the value of what I was cheated out of which was R95, 47 & that it would take up to 5 days to occur. 4 days later, I was refunded R19. When I queried it, they said, they can't refund me because I only had 48 hours to ask for a refund, but it was them who told me to wait 5 days for refund. I have screenshots of them promising me the R95 refund