[2020] New Phone - Transfering Accounts

Hoping someone has similar experiance, or someone at CG/EA sees this

Have an iphone, getting a new one in a month. I have an old SWGOH account attached to game center that I no longer use. My current account is off gamecenter and I'm assuming just attached to the phone.

How would I go about deleting the old account and attaching the new one to game center for when I switch phones? If this can't be done, how do I switch over the accounts.

Have looked everywhere, can't figure out a solution. Don't have any social media accounts.