Sorry to hear this bro.
I had almost decided to abandon this issue until I found this thread. Went through online chat as a previous poster mentioned (Had to select US site as UK wouldn't let me online chat) and it ended up being very easy.
Transcript for reference.
Agent (14/01/2022, 21:14:40): Thank you for contacting EA HELP, my name is Agent, may I start with your first name please?
My Name (14/01/2022, 21:14:45): My Name
Agent (14/01/2022, 21:14:56): Hi there, nice to meet you and how may I help you today?
My Name (14/01/2022, 21:16:01): I used to have my EA account linked to an old XBox account that I no longer have access to. I wish to link it to my new XBox account but I get an error saying it isn't possible. I have seen online that it is possible through live chat with you folks.
Agent (14/01/2022, 21:17:11): I will surely help you as you shared that you want to link a new Xbox ID to your EA Account as the old one is inaccessible.
My Name (14/01/2022, 21:17:25): Thank you
Agent (14/01/2022, 21:17:43): Please share your email address associated with your EA Account.
My Name (14/01/2022, 21:17:53): <EMail Address>
Agent (14/01/2022, 21:19:00): Thanks and allow me a minute to help you further by checking the details on the account.
Agent (14/01/2022, 21:19:30): Just to inform that the platform account needs to be free and not linked to any other EA Account in order to link it with this EA Account.
My Name (14/01/2022, 21:20:09): It is not linked to any other EA account
Agent (14/01/2022, 21:20:47): Thanks and do you have access to the email address you shared with us in the chat?
My Name (14/01/2022, 21:20:53): Yes
Agent (14/01/2022, 21:22:30): Thank you for the information, I have sent a verification email, please check if you have received an email with the subject line "Verify ownership of your EA Account" in your Inbox or SPAM inbox.
Agent (14/01/2022, 21:22:31): Please check and confirm here with the code.
My Name (14/01/2022, 21:22:44): <Verification Code>
Agent (14/01/2022, 21:23:23): Thanks and you may try and link the new Xbox account now using the steps in the link below.
Agent (14/01/2022, 21:23:33): https://help.ea.com/en/help/account/link-your-console-accounts/#how-to
My Name (14/01/2022, 21:24:04): Thank you I will give it a try
Agent (14/01/2022, 21:24:29): Sure, and let me know once done.
Agent (14/01/2022, 21:25:46): Were you able to link it?
My Name (14/01/2022, 21:26:06): Yes
My Name (14/01/2022, 21:26:12): All appears to be working
My Name (14/01/2022, 21:26:20): Thank you very much for your assistance