I need legal advice.

My old work gave me a key to the building.
They laid me off in the slow season.
1 month after they called and asked for the key back and I said I'll drop it off when I can.
I lost the key.
They keep calling but I blocked all the numbers from them. It's been about 4 months. I haven't spoken to them since that first convo.
Blocked calls but you can still get their voicemails. They are threatening to call the cops unless I return the key.
Advice?
Cops will never find me. All they have is an address to house I now lease and my phone number where they can't get through.