It sounds like you would be downgrading to our basic Email Plan from our Email Plus Plan. Some of the big items you would lose with downgrading is our Plus Campaigns: Events, Surveys and Polls, Donations, and Coupons. You would also lose the option to have more then one login user on your account. Other features lost with downgrading includes a/b subject line testing, dynamic forms, and the option to have more autoresponders than the welcome email that comes with every account. In fact, here is an article from our Help Center that goes over the differences between our two email plans.
If you have any further questions on your billing, please give a in to our Billing Department and one of our billing agents can help you get the answers you need. Thanks!