Free dlc not accessible without purchase

ok, for refunding try the following.

Go to https://account.microsoft.com

login to your microsoft/xbox account

Click on "Payments and billing" --> "Order history"

This will bring you to this page: https://account.microsoft.com/billing/orders

Here you will find the game you have bought, with a button "Request a refund" (see example picture)

No I have not, I have got on disc I only bought the "DLC bundle" digitally.

I am not sure because the GOTY bundle contains the original game and all dlcs for the game. Microsoft also sells a "DLC bundle" bundle witch cost the same as the GOTY edition and contain all dlcs minus the multiplayer ones and the original game. If I knew
this at the time of purchase I would have gone with the GOTY edition. Is there a way to get a refund or just add the multiplayer dlc to my account so I can dowload them?

If you have the GOTY installed, go to the game tile, and then go to settings using the controller to manage the game.

Go to installs, and see if you can download them there, most in game DLC with GOTY versions, just need to be downloaded not purchased.

do you try throught in game store??