Please refer to the examples below on ways to change the account you've linked.
Example 1: Changing linked account from X Account A to X Account B
Step 1) Link to a different account (Google/Facebook/LINE Account/Apple ID/Phone Number)
Step 2) Unlink X Account A
Step 3) Link X Account B
Example 2: Changing linked account from a X account to a Google account
Step 1) Link Google account
Step 2) Unlink X account