Vodacom refuses to repair device under warrenty

My Sony Experia T3 handset developed a network problem so i took it in to Vodacom Vanderbiljpark on the 05/04/2016,After waiting for nearly 2 weeks with no updates i decided to call them and find out if it has been repaired,She then told me that unfortunately the phone is void due to external cosmetic damages to the device (touch pad had a crack) they will not be able to repair the the network problem and quoted me R1850-00 to repair the device.Now having loads of electronics experience and asking 3rd parties we have all come to the conclusion that the external damage can in no way effect the phone from network problems in anyway.It's like taking a car which engine just gave in back to manufacturers for repairs and they refuse to fix it because the door has a scratch on it...I have been a loyal customer for 15 years and have easily spent hundreds of thousands rand's with the company only to be treated like this??They are charging over 300% more for repairs then other providers and if customers don't like it they void the warranty.I am beyond upset at the lack of service they provide their loyal customers and shocked they still in business