Vodacom Mayville bad service

I have sent my iPad for repair which took them almost a year to fix it. there was no update unless I went to check. I was given lame excuses every time I visit. when it was eventually fixed I took it home and the following day it starts showing lines on the screen. I took it back and the guy said i can help i have to again because when I took it the previous day it was working and they have no guarantee on the workmanship. I was also asked to pay in cash which I think it makes it difficult to calculate tax