Thank you for your answer. I did read this article and manual you are referring to before posting. My "friend list" is empty, "send SMS" to avast is off (both on the phone and on the website", "continuous tracking is off", sim card is on the "trusted SIM list". I uninstalled Antitheft but it kept sending the messages. I reinstalled Antitheft, "friend lis"t is empt and Antiteft disabled. My phone is connected to Avast web account and it shows there as well, that Antitheft is switched off. I am still using Avast Antivirus. The "New IMSI Messages" are still coming. I could not find any answer to my problem on either Google or Avast Forum. It all started just out of the blue. Any ideas.
Thank you again.