damaged s4

I have a s4 on contract from Mtn an I just loved my phone until it fell an the screen cracked.I was told by Mtn to take it in to the Samsung care center which I did an they took about 5 days an fixed my phone. But 2 days later the phone stopped working .it went dead an blank. I took it back to them an they were going to let me know what the problem was.2 dys later I was told the mother board was faulty /damaged an that they were sending it off to the Durban Samsung center. 10 days later I was told phone is ready .when I went in to fetch the phone was still not working