Dropped iPhone 5c, turned off, got really not, now unresponsive

Hi.

My Iphone 5C fell from a chair onto carpet. It did not crack.

It turned off immidiately and became really hot at the back. I left it to cool down.

After a few hours the heat went away. I tried to charge it since but it has not come back on. I tunes does not recognise the device.

I have repaced batteries, screens, cameras, and other parts in other Iphones so have tried to check if anything inside is obviously broken but can’t see anything which is loose or dislodged.

This is about where my experience ends.

What can I do next to repair the phone?

Thanks