Mobile sending SMS messages to itself

A number of SMS’s are being sent from my mobile to my mobile, plus SMS’s to the Czech Republic, at exactly the same time. This has happened a number of times.

This same issue has occurred with two mobiles I have.

There is just record of these calls on the Telephone company invoices; there is no record of these SMS’s outgoing or incoming on the mobiles.

Any ideas would be most welcome.

https://forum.avast.com/index.php?topic=193825.0