MTN Swaps out cellphone parts

I sent my Samsung S4 16Gb LTE for repairs after battery had swelled and damaged the phone (Known Samsung S4 issue) Battery was replaced but Phone came back (after 2 weeks with no phone)Damaged. Outer cover now had dents and scratches. I complained about this and they re-booked the phone. After another 2 weeks phone came back with new outer cover but Internal memory had changed from 16Gb to 9.28Gb. Phone had apps i had never installed and text was hazy when scrolling. I told MTN that this wasn't my Phone. They had to rebook it ..AGAIN and i get a call from someone in their service centre telling me that my apps were using the other 7Gb that had disappeared. Not withstanding the fact that you have to \wipe"your phone when it goes in for repairs. The tech tried to make me think My apps used up 7GB of internal memory and that's why it was not visible. So its 6 weeks with no phone now and that the service i am paying for. This is absolutely ridiculous as the Samsung tech at Clearwater just said to me they changed the board and put in a different one. So effectively the phone I'm getting back ain't mine. """