There are two options with Innovative Merchant Solutions and online payments. You can use Innovative Gateway Solutions (not recommended for multiple security reasons), or you can use Authorize.Net. If you choose to go the Authorize.Net way, note that you will need to get a different type of account.. a type 0 (zero) account, which will in all likelyhood cause the current account to be closed and a new account to need to be opened.
Ahh.. the joys of IMS's awful policies and lack of fully trained and informed personnel.
Good luck.