CELL C store horrible customer service

on the 5th of may i went to cell c store at ilanga mall in nelspruit to do an upgrade. the phone was found to be defect by the sales person right there in store, and they said it was the last handset. so, they had to do an upgrade reversal, which they did. I was told to come back the next day to upgrade on a different divice which i wanted. On that day, when i got home my sim had all the airtime, data and sms wiped to 00 and the sim was not working anymore. I went back to the store the next day to do an upgrade but i was told that the system had an error and the technical department had to fix my account. I have been going to the store since that day till today with no success. What a horrible service. I no longer want an upgrade, I want my refund for this month and to terminate this contract. I am done wasting my time going up and down for nothing. This is an act of poor customer service from cell c stores.