Blackberry phone unusable

I upgraded my contract in December 2014 and have had numerous problems with the handset that was given to me.In January the hanset was booked in at Vodacom Gateway Umhlanga and several repairs were done.A few weeks ago the keypad stopped working and it was once again booked in at Vodacom.The assistant at Vodacom advised me that the handset model has various problems.Why would Vodacom supply this model of Blackberry knowing it had problems.Yesterday I received a call advising me that moisture or water damage was the problem and I needed to pay R1400 for a refurbished phone which is crazy.There has been no negligence on my part and I was given a phone that does not work properly and it should been exchanged for a new one.I have been a Vodacom customer for many years and have various cellphones and tablets on contract which I will now move to MTN as this is unceptable to give me a hanset that does not work and then ask me to pay for a refurbished one.