Game Center login still allows "guest" access from hacked device

Product: Star Wars: Galaxy of Heroes
Platform:Apple iPhone
What type of device are you experiencing the issue with? iPhone X
OS Version 14.5
Ally Code: (Find it here: http://bit.ly/AllyCode ) 981-425-296
What type of issue do you have? Other
How often does the bug occur? Every time (100%)
Summarize your bug Even after an account has been secured to a Game Center account, another party can continue to log into the account. In my case, I had a security breach that led to someone gaining access to my account and transfering my account using facebook. I have since worked with the general EA help to remove my facebook linking and associate the account with an ios Game Center account, but the other party continues to log into my game and grief/destroy everything they can on a daily basis.
Steps: How can we find the bug ourselves? Transfer a guest account to another device. Take the guest account and associate it with a Game Center account on the ios. You can log into the account from both the new Game Center account and from the other device as if it was still a guest account local to that device.
Connection Type Wifi
Please select your region North America
Country United States

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I'm trying to do the right things to get my account secured, but it appears that the person who hacked me and attempted to steal my account still has access.

When I log in each day, I continue to find that they log in, spend all my resources (wasted 8k crystals on name changes) and try to destroy anything they can such as salvaging all of my gear.  

I worked with the general EA support to get the account associated with a Game Center, but the hacker still has access?  Is there any way to ensure that the account requires the proper login so I can keep them from logging in?

Ally code: 981-425-296