Alcatel Idol4 (?) - unlock google account from a phone??

I am looking for a way to unlock a google login on a phone - alcatel Idol4 (I think). I purchased the phone from kijiji last year, and hadn't used it until now. Since then I have forgotten the passcode and so I did a factory reset, not realising it is still linked to the old google account. I don't know how to break it out of this so I can use it. I have done many searches on the internet how to accomplish this, but none of them seem to work. Any ideas?