An advertising banner pops up on the site?

Question

JavaScript

Good afternoon!
There is a website on VP - xn--80aegbakpvmvl3a8i.xn--p1ai/. The theme is self-written.
The client periodically pops up an advertising banner on 2 different phones.
Moreover, the banner pops up without any regularity, sometimes it can pop up from the first boot, sometimes from the 30th.
I myself could not catch the bug, I checked it on many different phones, I tested it through the browserstack.
The site is without viruses, no left scripts loading the banner were found, specially re-uploaded all wp files and plugins, all js and css scripts. I think that the problem may be on the client's device, but it's embarrassing that it is on 2 devices (ios and android). What can be wrong?

Answer 1

These are cellular operators introducing their advertising.
Switch to https - solve the problem.