iPhone died in the middle of an update

My iPhone6 needed updates, and was low on storage space, so I started an update through iTunes. It crashed in the middle and said it couldn't complete. Now it's stuck in a frozen state. The screen is black and says I should plug it in to my computer/iTunes to continue. But it doesn't work. I've turned it off and on again. Same thing. I reached out to apple support and they're trying to call me but they can't call me since my phone is dead/frozen. How on earth do I get out of this mess?

Suggestions are to update iTunes before I can continue. But my computer is old and can't support the new versions of iTunes or operating systems. It's a 2009 MacBookPro. It seems I'm stuck.

Anyone have any hope to share with me?

Thank you.

GratefulTina