Seriously damaged tablet

On the 4th of January 2016 I took my Galaxy Not10.1 2014 edition tablet infor repairs under gaurentee at Loch Logan waterfront in Bloemfontein. I recieved it back just more than a week later, just to gind out at home that the tablet was not fixed properly. I then took it back too the Cell C store at Mimosa Mall on the 17th of January 2016 and they returned it to the repair center the next day. Up until now all so called repairs (even though they haven't been done properly have been don under gaurentee). On the 23rd of January I suddenly recieved a quote for almost R6000, telling me that the screen has been cracked and and the the main board needs to be replaced. When I enqyirwd they claimed that they have reviewed the tablet in that condition. I was clearly not responsible for the damage to the screen. Every time you vall them for some info the are placed on hold for more than 20min. I then resorted to email an they only awnser the emails after several days, and always with a different excuse as to why they cannot fix the tablet. I have an email where one of the consultants confirm that a credit has been pre approved. Please sort this out Cell C