Mancosa's systems are a nightmare to navigate

I am very disappointed in Mancosa. I wanted to de-register due to personal reasons, but the email provided for cancellations is returning unsent. I did this on the 12th od December. I proceeded to try another email; study@mancosa..... that email went thru but no response. not to even say call us or try this new email address. Someone suggested I try to de-register online under 'Registrations' but again there is no option to de-register. Can Mancosa resolve this issue please and refund me my registration money!!