I bought the 2k version of Xbox series x and Xbox one , I have Xbox one and it says it...

Sorry but 2k has not announced cross-play for the game.

Since you have to pay for the game separately on both consoles I doubt they will have Xbox One and Xbox Series X crossplay.

Before someone says If you buy NBA 2K21 Mamba Forever Edition you get the Xbox Series X version. Yes, that edition bundles both the Xbox One version and the Xbox Series X version but is not a free upgrade or the same game.

It's very easy how to check which version of the game you bought. Check the game case. If it says, Xbox One & Xbox Series X|S, then you have the Xbox One version of the game. If it just says Xbox Series X|S, then you have the Xbox Series X|S version.

I think they have given me the wrong disc version

On the disc is says "Xbox One - Xbox Series X"

I believe this is the Xbox one version that is compatible on Series X

Because I'm sure the Xbox Series X disc should say "Xbox Series X" and not Xbox One

I have contacted the seller and awaiting a response but thank you for your help

It's important to know which game your friend bought.

I say this because there are currently three versions of the Series X/S game. Gta 5 Online, Gta 5 Series X/S and Grand Theft Auto V (Xbox One and Xbox Series X|S).

If he has purchased Grand Theft Auto V (Xbox One and Xbox Series X|S), which gives access to the game for Xbox One and Xbox Series S/X, he can play online with you as long as he downloads the Xbox One version, so you and he will have the same save and can play online.

If he is a Game Pass Ultimate subscriber he can download the game in the Xbox One version and play with you.

It depends on what you bought. If you bought the standard edition, then it only has the Xbox One version. If you bought the Ultimate edition, it includes both the One version and the Series S/X version. So if you only bought the standard edition, then you would have to buy the Series S/X version if you want that version. The One version will work on a Series S/X though.