Dissatisfied

I took my phone to the MTN store to be booked in for repairs. My phone only had battery issues because it was draining battery for example from 45% to 10%. The phone was perfectly working when I left it at the store. I went to fetch it today, because I didn't accept their quote. My phone came back, no working, not charging. And I refused to take it back. I demand answers from them and I want my phone back working like I left it.