Xbox gamertag linked to someone else's Microsoft account.

Here's the backstory to my problem. I created my Xbox account 10+ years ago on the Xbox 360 until the next gen consoles were released. When the Xbox One was first announced I thought it was terrible console and opted for the PlayStation 4. So I've been using
the PlayStation 4 since release up until now. I just bought an Xbox One X and upon trying to sign back into my Xbox Live account I discovered that my gamertag was linked to a Microsoft account I don't own.

Now after some internet searching I found that there apparently used to be a way to transfer a gamertag between Microsoft accounts. But, there isn't anymore as far as I know. The problem is I have a lot of purchased content on that gamertag that I'd be losing,
on top of game progress, if I just use another gamertag.

I contacted Microsoft and Xbox support but they say there is nothing I can do. Even though my digital property was essentially handed over to someone else by Microsoft, whenever this automatic merger happened, they say that "certain steps" have to take place
before you can file a fraud case and that those "steps" haven't been taken so they can't do that. They won't tell me what the steps are either.

It's worth noting that I happen to have access to the Microsoft account that my gamertag was linked to. Since I know the owner of the Microsoft account and reached out to them. They temporarily gave me access to verify and remedy the situation. But I won't
be able to simply take over their Microsoft account and change it all to my information. That's their property and they have their own content that they need from it. On top of that, the Microsoft account is a hotmail email anyway, so it can't be removed without
completely deleting the email address which means they'd lose access their email. But the Xbox account is mine and my property. Or was, I guess should say...

I cannot believe Microsoft doesn't have a solution to this problem anymore? How can Xbox accounts just be commandeered by someone else though an automated linking process and then not have a way to fix it?

If anyone else has any insight to help assist in this problem other than game sharing or deleting their email and me taking it over, I'd love the input.

Thanks,

Derek R.

:)