[Jovian Marwa]

every time I unlock my phone, a pop-up ad appears on my screen, and when I want to close it, it takes me to a website (www .zaka123. com / ....) then redirect me to another (m .letstravel. site/mobile), I have already done a factory reset and I have tried many antivirus, antimalware, airpush etc ... but nothing seems to work.
Sometimes a strange icon appears on my home screen, entitled "Travel".
No bizarre application in my application manager, and I think I have never installed an application from an untrusted source.
Help me please!