Are you the original owner of the device?
Do you have a Google account with the proper credentials to log in with?

 

Hi there, Blah!

How long have you owned this device? It seems to me that you're up against Factory Reset Protection (FRP), which is a failsafe to prevent lost or stolen phones from simply being reset and used/sold. The device is tied to its primary Google account, even after a factory reset: the legitimate owner has to approve the reset. IF your Google account has a phone number with which you are not familiar, it's possible that your login credentials were compromised. Change your password immediately to a long, complex password. Correct your alternate contact info in your Google account (which you said you did) - and perhaps send a trouble ticket to Google explaining the situation, If you are the rightful owner but your credentials were compromised and changed, there should be recourse to correct it.

It's also possible (though not likely) that the SIM has been hijacked by another number. Check with your carrier to make sure that SIM Lock is enabled: this prevents the SIM from being cloned & copied for any number other than your own.

Good luck and keep us posted!

 

One thing to add: you should remove your Google account from a phone before doing a reset. Otherwise the person you pass it on to will need your Google login credentials before they can use it, which you don't want.

 

Ninja'd - Better answers above ^
=======

Try going in to the Google app - Manage account - Personal Info - then tap the arrow by your phone number which will bring you to another screen where you can toggle things.

I'm not an expert here and it may be a blind alley, but I just found this now after a problem getting my bank to verify an updated debit card in December.

Others will help if that doesn't. There could be more than one reason, but I agree it's annoying.

 

What you are experiencing is Googles anti theft protection.
Which is a good thing because without it, anyone could take over your device along with your personal information and cause you very much hardship, waay more than what you are experiencing now.
Chalk it up as buyer beware moving forward.
Take the hit on the trade in is your best option at this point.

 

Yep, it seems as if the previous owner didn't fully remove it from the phone before returning it to Best Buy. And I don't buy things from that store because of its short return window.

The only thing I can think you can try is to call the unknown phone number and see if it's still the former owner: and ask if they can remove the device from their account.

 

The basic question remains (to help me understand at least)
... did you factory reset by removing your Google account in Settings?

What is the status of the phone now, ie is your account back on it?

Did you know another account was still on it, so did the reset via Recovery Mode - or were you told it's an open boxed, unused device by Best Buy - in which case it's their fault.

As per your initial post, has it only had your account on it. Did you have it a few days before your own number was ported to a new sim around that time?

Can you go in to Googles Device Manager and see if it is still listed there (although it used to take a while for an account removed device to disappear from your device list)

If you changed your Google password in an effort to fix this, then that takes 24 hours plus to become active.

I / we can only surmise what you have or haven't tried, and you may have found a chink in Google (which surprises me not one bit)

 

This doesn't give much details. Assuming that it is indeed your own personal Google account that's on the phone, there's absolutely no reason that you shouldn't be able to change the recovery phone number or email that you have on file. So when you say "to no avail", what error message is it giving you when you try to change the phone number?