Annoying poor service

I bought a device A12 Sumsang from Vodacom in Durban the one in West Street then after few days I realised the speaker of the phone is faulty, the person on the other side can't hear me, then I returned the it to the nearest Vodacom shop in Richards Bay. They took it for repairs then today they called telling me that my phone is back but not repaired because I used another network on the device. I must come fetch it and take it to repair at my own expense. That stupidity, why should I pay for my repairs. Who buys a new phone and use the phone that has been to repairs. I'm so annoyed yhooo!