Google Sitelinks are not the top-level pages in the menu, how can this be changed?

I have a client who's website ranks well but they are unhappy that when people Google their brand name, the sitelinks under their domain include random pages such as About Us and Contact instead of the top-level pages in their menu.

Does anyone have any suggestions for some updates I could make to encourage Google to list the more relevant pages over generic pages?

Thanks