I cannot install any mobile antivirus programs on my LG phone

[AC Question]

I believe some malware was installed on my phone when I went to to a site to check road conditions. Some text messages have been followed by a negative version that I did not type or send. I went looking for an antivirus program, and have been unable to install Avast, AVG, Kaspersky. All get either "an unexpected error has occured", or just not installed, even though the page says the app has been installed. None of the apps show icons or are listed in App Mgr.