Chinese Adverts

[AC Question]

I am trying to get rid of an annoying Chinese ad page that pops up regularly on my phone. My phone is an OneplusX bought online from China and is a great phone apart from this annoying ad. It does not appear when I am browsing on the internet, but is regularly on my phone when I open it up making it difficult to answer calls. I do not think a browser Ad Blocker would work and I tried an App Ad finder which did not work. From researching I understand that it must be an app that is bringing up this page, but I cannot find it and I do not want to try and root my phone. Can you offer any assistance?