Your hosting plan determines the services you get with the account and the prices for these services. Big sites with high hit rates and special services require more expensive plans; cheaper plans are suitable for simpler sites.
To change to a different plan:
Warning: Switching plans will disable the resources that are unavailable under the plan you are switching to.
If you don't see the plan of your choice in the list that appears, it means it is incompatible with your current plan. You can't change to an incompatible plan, but you can create a new account under this plan and then, if you want, you can delete your old account.