Mobile phone?

So; you want us to suggest how to unroot a mobile phone but, fo rcome reason, you decided we didn't need to know what the make or the model was - hell, even whether it is an Android, Windows, iPhone or something else entirely!!!

On the face of what you describe, I guess you own (but don't know how to use) an Android phone.

Let's say it is a Samsung S3: Why not simply start with a Google search for "samsung s3 unroot"

Then check you understand all the steps involved BEFORE you do anything.

You could even sign up to the relevant make/model forum at http://www.modaco.com or http://forum.xda-developers.com/

http://xda-university.com/as-a-developer/introduction-how-an-android-rom-is-built

They may even be able to help you remove the infection, which appears to be Payment Cola.

http://virus.nq.com/en/android/a.payment.Cola.a/

You've got some learning to do
September 2015