I 've just recently bought secondhand Pro 5, unfortunately I got this dreaded error "You have not logged out as okolopo63@flyme.cn. To use another Flyme account, please log out properly first."

I tried to contact the seller and he had purchased the phone from previous owner and don't really care about using flyme account and suggested me to skip Flyme account screen.
The reality is I need Flyme account to gain root for me to restore apps from my old phones with titanium backup.

Reading one post in this forum that suggest someone with the same situation as myself, I contact the mzcs@meizu.com to unbind my phone to okolopo63@flyme.cn.
My phone was originally came with global firmware, before I request the unbind process I was eventually able to flash my phone with chinese firmware 6.2.0.2A to test the nougat build for Pro 5.
When Meizu CS informed me that the unbind process was finished, I managed to login to flyme with my new account in chinese firmware.

To my surprise when I revert back to global firmware my phone is still bound to okolopo63@flyme.cn account.
I then emailed back about this situation to Meizu CS, and they check that my phone is chinese version and should be used with chinese firmware.
I'm totally confused whether Meizu have separate database to keep phone binding status for both international and chinese phone?
I intend to use my phone with global firmware cause I don't read nor write in chinese, even changing the weather to my country/city is chalenging as I can't even read/write it.

Can someone suggest me on how to unbind my phone in global firmware, or I have to live with this condition?