Pop up add

I have an iPhone 7 and a 6s that I use to go to this site. Before I can log in I get a pop up you have won a new cell phone. The pop up will not go away I have to close out and start all over. Sometimes 3 or 4 times before I can get logged in. This is the only site I have this trouble with. Is there something I can do. I have block pop up adds on.

Pop up add