Working with Spamhaus

Hello All, SpamHaus has done us the favor of blacklisting all of our prefixes due to the issues with handful of IPs from customers we have removed from our network. They are now being unresponsive on helping us get these listings removed and we have a lot of legitimate customers who are no longer able to send email. If anyone has any advice on how to deal with these people. Please let me know here or off list. Thanks!