Uninstall old version of anti-theft

[REDACTED]

I have marshmallow with Avast Mobile Security + anti-Theft. My original SIM card died and I replaced it, but Anti-Theft activates and sends a text to my friend every time I re-boot the phone. My friend is getting tired of the messages and I can't figure out how to get Anti-Theft to like the new SIM, so I figure the best way is to uninstall. But how?

I found a link to this FAQ on another thread:

https://www.avast.com/faq.php?article=AVKB166

but it doesn't seem to work anymore, it just links to the general FAQ page. I have a vague suspicion that I've got to do something like change some phone settings before I uninstall.

On the other hand, is there a way to make Anti-Theft accept the new SIM? I can see myself in another country buying a local SIM and using it in my phone and I'd like Anti-Theft to accept it.

Thanks!

[Asyn]

Enter your Avast-PIN to whitelist your new SIM.