Hi Golam,
it seems like the difficulty you find is communicating the value of your work to the client,
If I were you I would focus on the initial brief. It is not up to the customer knowing (or being able to express) what he wants or what is most effective when it comes to brand identity: he can give you some suggestions about his personal preferences, but you are the professional and it is up to you to propose an effective logo.
The initial brief is very important because it collects all the information needed to better identify the business profile, which will allow you to build a basis from which to start to create a logo that is an excellent visual representation of the brand AND it is also effective, and successful.
Have you considered preparing a list of preliminary questions? I use a small questionnaire, and over the years it has really made a difference.
Good luck and good work! 🙂