Note that if you change ISP you will lose your current e-mail address.
You will also lose all your current e-mails.
Anybody who sends you e-mails, or any company or web site you are registered with, will not have you new e-mail address.
Write down a list of all the people who send you e-mails (be they individuals or companies) and when you get your new e-mail send them a note or update your profile on their web site.
Also if you have an information in your existing e-mails like passwords, web site details etc make sure you write it down, or maybe print off important e-mails, so that you can use it when you set up your new e-mail system.
You may be able to get it set up so any mail sent to your OLD e-mail adress will be forwarded to your NEW e-mail address.