Paying 1 company for a domain and it's registered with another?

I’m a bit confused on this. I’ve been paying donhost for years for a particular domain, though apparently it’s registered with fasthost. Can someone explain for me how this kind of thing works? Is this just reselling?
Do Donhost just pass the money I pay (less a little cut) back to fasthost? And when I make changes to the whois or nameservers, does anything happen at donhost or do they just pass it to fasthost?
I’m getting into a bit of a dispute with them but don’t understand the setup here.

‘Donhost’ will be just a reseller of fasthost.
If you are in dispute, it will be best to transfer your domain immediatelly to another domain name registrar.
If you are hosting also with ‘donhost’ then change host also and migrate your entire hosting account.

Please check whether you have full rights of your doamin or not, whether you can obtain ‘domain secret’ or not.
Good luck.

As rule it is more cheaper to buy domain name from reseller instead of domain name registrar they are reselling from.

There are a lot of “domain” suppliers who just resell domains that they get from a domain registrar. As a registered reseller they get a discount of the domains they get from the registrar and so in some cases can undercut the registrars retail price and still make a profit.

Strange, I’ve got clients who have their domains with Donhost and they are registered under Webfusion (S2 Consulting)