My phone is an ANS UL40, running Android 7.1.1. A couple of weeks ago, I started noticing that every time I turn on my phone or wake it up, the first thing on the screen is a page trying to get me to play/buy a game, with some ad for something medical or age-related (I'm 55). When I close it, I then see my usual wake-up screen. The name on the app is "seamax" but I can't find that in my app list. And when I google "seamax" all I find is websites for airplanes and boats. Clearly this is some kind of spam and/or virus. How can I get rid of it?