Although I can issue a full refund thru WePay I can't seem to do a partial or full through C.C. The link for CC's Knowledgebase article btw is incorrect, but I could find the correct link in WePay support - however updating the API is beyond my skillset.
I apologize for any inconvenience. I appreciate you letting us know there is an issue with our Knowledge Base article. If you could let me know which article it is I can inform the Knowledge Base team. However, Constant Contact does not handle any payment processing for events. It is processed through WePay or PayPal. In order to get the help you need, I recommend contacting WePay's support team for additional assistance.