****EN ****TY ****MERS WITH THEIR MERCHANTS

I have placed an order with debonnairs pizza, and I got the message a juice was out of stock I should replace it within 10 minutes and when I went to the app to accept or replace the item out of stock, I picked the one that was lesser with amount to the original juice, then when I clicked on accept/replace the ****en uber eats charged me the full order amount, mind you initially they took R159.00 for the whole order total, now for me to get the item replaced, they charging me yet another whoopping R159.00 cool, I had nothing more that R159.00 so the replacement was not successfull until the countdown timer was lapsed, then the order was automatically cancelled, by the flipping merchant, debonairs, then I had to order with my other bank card details, order was successsful. Now I want to know why is uber eats not refunding me my R159.00 for the cancelled order? I have contacted them onn the app they say 48hr passed they can not assist,now tell me why uber eats charges full order amount for the replacements? and why they can not refund me?