I phone 6 four months repairs???

I have a iphone 6 that stopped charging in December. The problem is that i cant switch it on to disable find my iphone. I have explained to them the problem then they sent it in and a month later i fetch it and they have done nothing. I have sent it in now for the 4th time? What needs to happen in this case?????? The phones warrantee has expired now but it was sent in the first time before it expired. I am now sick and tired and need this phone back next week or a replacement unit.