I bought minecraft on the nintendo switch. Could I refund the nintendo switch one to get it...

You'd have to check what Nintendo's return policy is to see if you'd be eligible.

By a switch I meant a Nintendo switch and when I get Minecraft invites instead of going to my Nintendo switch it instead goes to my mobile account on minecraft

Hello JuleN95 sorry the content is unable to be found at this time you can try this to see if it all show up.

I own Minecraft: Nintendo Switch Edition and I’ve bought previous DLC. How do I get it to sync to Minecraft?

1. Log into Minecraft: Nintendo Switch Edition on your Switch account. This will sync the latest purchases.
2. Log into the Minecraft on your Switch and you’ll be automatically granted the entitlements for that DLC.
   

Note For every purchase you make on the previous version, you must first log into
Minecraft: Nintendo Switch Edition, exit, and then launch the new Bedrock version for purchases to sync. DLC purchased within
Minecraft: Nintendo Switch Edition will only remain on your Nintendo Switch device and will not carried over into other devices.

If still need further help you can visit this Minecraft for Nintendo Switch FAQ to get further information.

Thanks

We recommend checking this => Minecraft for Nintendo Switch FAQ – Home. You could also restart your router to troubleshoot the issue. If the link provided wasn't helpful, it would be best to get in touch with the Nintendo Switch support for further assistance. Keep in mind that this could also be from the game developer's side so might want to check with them as well in case there are no issues with the Nintendo Switch.

Have you an active Nintendo Switch Online Subscription? I ask this because I found the following Q/A on Minecraft Nintendo Switch FAQ:

Can I play Realms on this edition?

Yes, Realms is available on the Bedrock edition of Minecraft for Nintendo Switch. To play online on a Nintendo Switch, you need to have a Nintendo Switch Online subscription, so this is a requirement for playing on Realms. More information about Nintendo Switch Online can be found here.

Furthermore, can you post the entire error message (better a screenshot/photo)?