As a result of getting unexplained SMS's sent to the Czech Republic, I researched and found that it was Avast Anti-Theft that was the culprit.
It seems likely that I received an email from Avast on each occasion it sent an SMS. That email just told me the location of my phone with no explanation as to why it was being sent, and so I ignored them.
It would be helpful if the email said that it was as a result of a SIM change and that an SMS had been sent to Avast to trigger it.
It would also be helpful if the system didn't keep sending SMS's at random intervals from one SIM change without checking that this was desired.
If the email went further and said how to mark the phone as "Found" in the profile (or whatever is the next best step), that would be even better.
