Worst service at Huawei Canal Wal****

I had the worst service experience at Huawei repairs center Canal Walk. When I booked my phone in for repairs they asked me to pay R150 fee which was fine and then they would charge me the repair costs after i get my phone fixed. It took me going back to their store 3 weeks later after waiting for a quote on the work to be done on my phone for them to start working on the phone. After that it took another 4 weeks for me to get my phone back. I realised then that they overcharged me so I asked to be refunded . I was told because I paid the R150 book in fee cash so I cannot be reimbursed since there is no proof of payment????I could not believe my ears. They sent me an yoco invoice with a zero balance when i booked the phone in and a R1350 after the repair was done. Am I responsible for their staff members not doing invoicing properly! So I have been emailing back and forth with this people since February and they're still saying they won't give my money back. Worst service and on top of that they ***** people money!!