security - Trojan & Malware removal

I have a Samsung Grand neo I9060, in which I recently downloaded an app from the web only for it to install malware and trojan in it. Each time the data connection is on or I'm connected to a wi-fi pop-up ads frequently appear which is pretty disguting. Efforts to uninstall this malware via apps from play store have all been futile. The device is not rooted. Kindly assist if you can, please.