Hello Dewbyeyou1,
Welcome to the community!
Sorry to hear you're experiencing this issue. That does sound like a rather concerning situation. I understand that your virus checker did not find any viruses, however, that behaviour definitely sounds like a virus or some malware has infected your device (see here and here and here).
While a factory reset does indeed manage to remove some viruses, doing so might not remove all viruses (see here and here). It depends on what part of the device the virus was able to infect (see here). If the factory reset did not effectively remove the virus or malware, it might be helpful to try to get some additional information, if possible. Did your friend note the content of those text messages? Were they all the same? Googling the message content may lead to a possible virus or malware culprit. Once identified, you might be able to search for more effective means of removing it.
Did you back-up your phone before the factory reset? I understand that you might have had important information on your device. However, before restoring your back-up, you should consider that any virus or malware could be a part of that back-up.
Hope this helps 😀
Cheers
