Vodacom damaged my phone &want to charge me for it

I took my phone to the Vodacom shop in the George mall for repairs because it would not allow me to make calls or send smses when I put a Telkom sim card in it. It is still under warranty and I was assured the repair process would not incur any costs. It had to go through to JHB and now over 2 weeks later I get told the charger/USB port is broken and I have to pay R2293.35 to have it fixed and if I don't accept this quote they will send it back without any repairs!! It's either fix everything or fix nothing!! This is ridiculous and unacceptable, there was nothing wrong with the charger/USB port when I sent it in, I was still using the phone and transferred photos onto my computer a few days before taking it in, I can prove it. Plus I have my slip they gave me at the Vodacom shop stating the problem that I checked it in for. Whatever damage there is to the phone happened after I took it in and Vodacom needs to take responsibilty for it. I want my phone back asap, in the good working condition that it was in and call block taken off. Vodacom's service has really gone down the drain and actually don't want to deal with them anymore.