Yello Appauling Service

On the 7th of March 2014 I upgraded my phone to the Sony Experia on the 4th September the phone switched off and wouldn't go on again. MTN then replaced the phone on the 14th of October the new phone did the exact same thing. To make a long story short after 5 months and blameshifting by MTN I recieved the phone back on the 20th of January, low and behold the speaker was broken and it is not picking up signal. I have send numerous emails made just as many phone calls. When i phone customer care they say i must phone high volume repair centre when i phone them they say no i must speak to customer care. Out of desperation i went to an mtn branch to hear if maybe they can help me. I was told that i must go to Sony directly and sort out the repair myself as i am fighting against MTN's wallet and they don't care about an individual customer. This morning i tried phoning customer care again, while i was still talking to the agent my call was transfered mid sentence and then cut off. I dont want the phone repaired again. Out of the 8 months since my contract was upgraded i could use the phone maybe six weeks. All I want is a Nokia Lumia or a Samsung S4