Hello,
we informed you about the international SMS during the registration process with the my.avast.com account.
Starting with the next update of Anti-Theft you'll be able to disable the sending of these SMS. If you disable this option, our online portal won't know your phone number in case of emergency.
we need to send these SMS since a phone actually doesn't know it's own phone number. It only registers in your carriers network with the IMSI. To get the phone number, we need to send a SMS to our server.
regards,
Werner