Phone still not fixed

I sent my iPhone in for repairs as it was showing me black screen when I switched it on. I sent it in on the 20th of March at the in Vodacom Cresta and to date my phone is still not repaired. I then received a call from Vodacom Cresta yesterday notifying me that the Vodacom Repairs center cannot fix the phone where they further then told me I should take it to Vodacom Clearwater Mall where I signed my contract to be repaired as the screen is faulty - this does not make any sense to me. This customer service is so poor, I currently have 3 contracts with Vodacom and I have been a loyal customer for the past 10 years and you cannot even fix my phone that is currently under warranty and it is not even a year old but they are so quick to sell me a contract with a phone that does not even last a year. I have not collected my phone as of yet from Vodacom Cresta and I cannot wait another 3 weeks for my phone to be fixed. Kindly advice further as I am not going to go collect my phone at Cresta to take it to Vodacom Clearwater where the same processes should be followed.