I am a reseller through a small time provider. I have my own name servers so i am set with anonimity there.

one problem i am having though (and my provider doesn't know how to fix...) is that if a customer goes into cPanel by using the www.domain.com/cpanel method...then it redirects to myprovider.cpanel rather than mycompany.cpanel.

is there any way to fix this? or make the /cPanel not work and force them to login cpanel via cpanel.mycompany.com?

Yes, under the Tweak Settings there is an option that needs to be unchecked:

When visiting /cpanel or /whm or /webmail with ssl redirect to the servers hostname.

and

Always redirect users to the ssl/tls ports when visiting /cpanel, /webmail, etc.

Your host should have all resellers on a box with a anonymous hostname regardless.. No matter what someone can typically lookup your host regardless if they want to waste enough time doing it but using an anonymous hostname I would say is bare minimum if that.