Welcome to WebmasterWorld Guest from 18.104.22.168
I assume you mean changing the name servers listed for the domain?
It depends on where you registered the domain whether you can change it yourself, unfortunately if you leave it where it is you will have to continue to deal with the same people. Some registrars provide tools for managing your domain(s) which includes parking it until you are ready to use it.
Some advice (I know you didn't ask for it - so take it FWIW)
Make sure the domain is indeed registered to you by doing a whois query. Their stalling tactics don't sound good. If it isn't then you have very little control over it. At the very least you should be listed as the administrative contact, but it is usual to also be listed as the billing contact.
You can park your domain in lot's of places these days, graitecanyon.com is a public DNS service where you can map your domain to DNS servers (i.e. park it) until you are ready to use it, then you can simply change the DNS entries to your host's name servers once you decide to host it somewhere.
The guy hadn't gotten back in touch with me within a month, so I had the client talk to him.
I think sometimes people get offended, like it's my fault that the client doesn't want him to be the contact anymore.
If you have the password for the domain, you should be able to aubmit the change request directly through bulkregister.