Yes, we can change the main domain on your account, but the account username must remain the same. Simply visit http://requests.pacifichost.com/ and choose the form to change your domain name.
Please make sure you don't have the domain you are changing to used anywhere on the server (addon domain or parked domain or cpanel account). If you do please remove it first before issuing the domain change request.
Please note: If you have addons domains created within the cpanel account they may not show in cpanel after the domain change, but they still will function. This is due to when you add an addon domain, it sets up the addon domain AND a subdomain. This is how it keeps track of the ownership. Since you changed the main domain, it no longer sees them together, so it doesn't list them anymore, yet they will still work fine.