I got charged for a FREE game!!!

Wrong. A sales transaction requires two participants - the buyer and the seller. The seller makes an offer, and the buyer ultimately agrees to the offer. It's up to the buyer to make sure they agree to and understand the terms of the offer. That's why
the purchasing process on the Xbox Store has two steps. One is to say you want the content, and the other is to say you confirm that and agree to the presented terms. Each and every time I claim a free game, I make sure that the price is indeed free. I've
seen it where it isn't, at which time I back out of the deal and try again later.

I trust Microsoft without question, but I also verify what's on offer.

Unfortunately, you're way past the dispute point for this transaction (maximum of 14 days), as well as with your payment method (most require a dispute within 60 days). When you were claiming the game, did you see a price displayed, but you proceeded anyway?
Was your Gold active on that date when you completed the purchase?

Hello Xbox Ambassador,

Thank you for replying to my post.

The game was purchased under the correct account.

Transaction date: Feb 27, 2019

Amount: $39.99 (Super Bomberman)

I've been trying to get it fixed for the looongest time to no avail

Feel free to verify the FREE game via this link

https://en.m.wikipedia.org/wiki/List_of_Games_with_Gold_games

For a refund you will have to fill out the form located at the following link.
https://support.xbox.com/en-US/forms/request-refund

Also you must Delete your Credit card on your xbox if you do not want to buy anything.