Uber management and drivers rob us of our little cash

Saturday the 26th of December i requested Uber from JHB CBD to Newtown Junction. My fare was R22. i gave the driver R40 and asked him to put the change in my wallet of which he did not. Sunday the 27th i put a compliant on the site and was refunded he R18 into my wallet. Sunday the 27th i requested Uber from JHB CBD to Hillbrow and was charged R21. I was not taking the trip but had requested it for my mother. The fare was R21.So i made the driver aware that i had R18 in my wallet and he said he had no proof that i has R18 and i should pay the full amount of R21 as i wanted to make a cash payment before he left. So i gave him the R21 and when the trip had finished i realised the R18 in my wallet was deducted as well. When i complained again on the APP i was told i had made too many complaints and could not be refunded. These Uber drivers are robbing us of our hard earned little money in broad daylight and management supports that and does not refund when they know pretty well what their drivers get up to.