Frausters and rude service

I have previously complained about my phone which I took for repairs at cell c, after I had to flush everything on my phone since the guy at the store it could be the apps I have downloaded or software update. They took my phone for 2 whole months and gave me an invoice of about R2200 saying I needed to pay because according to them it physical damage and mother board. I asked if Im not under warrantee and they said no it doesnt cover, for me it was seem ridiculous coz my lcd was working fine so I askes that they should return my fone. I took it to another technician who said it was just the chargingbpin was faulty and it was fixed for merely R300. What sort of ******* does Cell C technician were talking about. No one from cell c even bothered to be in contact with me. It the second time I have had contract with cell c and both times the relationship doesnt end well. Worse of all one of the call centre agent when I asked to speak to a manager she said they is no manager on duty and her word was final. I need to take this further because it makes me wonder how many people are ********** by so called untrained technicians that are hired by cell c.