linked his Google play and mobile number

I recently returned to my PUBG Mobile account after a two-year absence only to discover that it has been hacked for about 4 months. The hacker has linked their mobile number and Google play to my account and changed my nickname, making it impossible for me to unlink them. Now he is able to login to my account when ever he wants and he can kick me out of my account anytime.

How can unlink them??