Malware persists after factor y reset

Hello,

Some days ago muy phone was infected with some type of malware. I get this malware through whatsapp.

What I did is a factory reset of my smartphone (Motorola moto g 3 gen). I am pretty sure that this malware is still in my phone, let me explain:

After this factory reset I re-booted muy phone. When I tried to navigate using chrome, suddenly a tab appeared with the symbol of google telling me that I was infected and I have to press a button (with a count down). I did not do it, but this is one of the reasons that make me think that the virus is still in my phone.

The second reason is my phone is consuming data all the time, even if I am doing nothing with it. I have tested this comparing the consume of this phone with another moto g (1 gen). The infected one never stops consuming data, more than 1 MB every 15 min. (more por less) doing nothing with it.

Then, my question is: what can I do to remove this malware from my phone?

I have just bought it, so I will appreciate any solution that involves to do not unlock the bootloader, because I do not want to lose the guarantee.

Thanks in advance.