I can understand how important it is for the billing on your account to reflect the correct amount. For your account security we are unable to go into your billing details here in the Community. Instead please call into our Billing Support for further assistance. One of these agents can help answer any questions you may have!
I also manage a non-profit and spoke to a representative from the billing department. I had no problem receiving the reduced rate after submitting the appropriate paperwork. It's always better to make a phone call. There's nothing to substitute for direct "contact" despite the fact that this company's expertise is with email messaging