How do I downgrade my linode pricing plan?

hello,

i create a website and use linode.
my website is simple with only a few clients.
i want downgrade my pricing plan from standard 20 dollars plan to 10 or 5 dollars/month plan.
i want to know how?
does it mean i should open another new linode machine, and transfer from the old to the new one?

or can i just change settings of current machine?

thanks very much!

Yours
Lupeng Liu