802.1x guest user with a 802.1x configuration (another domain)

Hello all,

I have an issue with some guest user who have a 802.1x configuration with their own companies. What happen is that the user who have 802.1x enabled try to authenticate with our NPS but the domain doesn't exist on our side. And there's a retry every minute or so right now. Is there a way we can denied other 802.1x with another domain? Make it ''normal'' guest user? Or it is on the side of the guest user?

Thanks