Many merchant account providers use the Authorize online payment gateway.
These include RTWare.net, MerchantCommerce.net and countless others.
If your merchant account provider is not on the list of those compatible with the
shopping cart, ask if they can use the Authorize.net network.
Often they can.
Questions about terms, rates or other payment processing issues
should be directed to the provider in question to ensure the most accurate answer.
Use the hosting control panel to tell the shopping cart which credit card processor (secure server) to use.
Select either Authorize, RTWare or MerchantCommerce in this case. Many other options are available to you.