How to terminate contract & secure refund?

I was sold a 'vhi' contract by John Bellardi and given the contact details of Lukas Muller, his manager at a presentation at the Irene Country Club on the 19th of October. Today, the 20th of October, I have phoned, sms'd and emailed Lukas Muller several times to terminate the contract without any response from him. The main office ( ********** ) has no clue who nor what I am referring to. What must I do to terminate this contract and secure a refund asap?