Why does my phone send foreign SMS i did not send?

I have nearly €5 of charges for “SMS naar het buitenland” to strange numbers to several countries where I don’t know anyone--Romania, Australia, Sao Tome and Principe, Switzerland, Equatorial Guinea, Spain, etc. All were sent August 6 and 8, but I can’t find any records on my device of having sent these messages. Simyo customer service, when I sent a screenshot of the charges, said this was a “flubot” and I should restart my phone from factory settings. However, I have an Apple phone and it looks like flubots can’t run on iOS? I’ve never clicked any links from unknown numbers, nor given any website my Apple ID information, as is described of typical of a flubot. If this is a problem with my device, it isn’t impacting my US eSIM--only the Simyo line, which I installed August 4 since I just moved to the Netherlands. I don’t think it’s a flubot, what could be the problem?