UBEREATS EATS PROMOS WITH NO EXPLANATION WHATSOEVER

I ordered food with uber eats , i had a promo which allows me R75 off from R100 purchase , i then ordered from Willy Wonka ( 3 pk donuts from krispy kreme and a tonic water 1ltr.) when the order arrived the driver then informed me that he was only given one item , upon further investigation i then found out that it was sold out however i was not informed , prior to this i experienced the same thing but was called and informed that there were changes .why in this case was i not informed , i have made numerous complaints and till now no feedback, also what happens to my promo ? and why was the promo still expired when the price of my order came to R47???????????????????????????????????????????????