Okay, I see there is a misunderstanding here.
You are obviously talking of your counterpart that sold you Check Point. In this regard, yes, I agree with you, they should complete all contractual obligations as written there. If knowledge transfer and documentation were promised and not delivered, do whatever you have to do, to get them done.
Now, earlier you wrote: "We have bought a support & maintenance plan with them. And when I opened a support ticket with them to say that we want to change admin password, they didn't clearly tell us how to do it. They merely "pointed" us to read the manual..."
I took it as you are blaming Check Point TAC for not helping you with the configuration. If that was indeed the case, please read your maintenance contract carefully. If that was not the case, and you are still talking about your third party seller, I am with you.
Finally, to make your journey with Check Point less frustrating, please take a look on our CP4B section, where we are posting quite a few entry level materials for engineers only starting to grasp Check Point solutions and tools. Here is the link to the list of currently posted materials: https://community.checkpoint.com/thread/9695-welcome-to-check-point-for-beginners
Hope that will help. If not, read the manuals and ask CheckMates