Ads or a virus;

Someone please help me.

It's been 4 months since my Iphone appears in the calendar app ads that look like a virus. when I shut them down, it keeps showing them on safari all the time! they're not leaving, and I don't know what are they. recently a friend of mine who also has an Iphone asked me what to do because the same thing happened to her! somebody answer me soon, thank you.