Vodacom refusing to fix and return my phone!

I would like to complain about the service that I have received from Alisom Vodacom Repairs. I am actually doing their work for them, they don't communicate or update on my phone's repairs. I had to call 2 weeks ago to ensure that my phone is being repaired. On Friday the 13th I received a text that my phone is in-transit, I called today to check on my phone only to be told that they are holding on to it until I pay the excess; WHEN AND WHERE DID THEY COMMUNICATE THAT IT HAS TO BE PAID FIRST?! And if I didnt call to check it means that I would have never known what is happening - absolutely unacceptable!!!