I found my old iPhone and I don't know if I can still use it?

When I lost my phone then ordered to get a new one, I charged my old one when I found it and its working, I'm wondering if it will get blocked if I connect it to the Internet, does anyone have a answer

Solavei.com/camelot1402

You can indeed just the sims cards at at&t are updated and you can't turn it off. It happened to me.