VHI non existent - or so it seems

On Saturday, the 17th of Feb 2018 my husband and I attended a presentation by VHI in Kemptonpark. Unfortunately on emotion we signed the agreement, but after careful consideration the next day, we realized that we actually cannot afford it. I sent them an e-mail on the 20th of Feb 2018, attaching a cancellation letter to inform them of our intention to cancel. Original documents were sent to them via Speed Services Couriers, which was delivered within the prescribed 5 day period. I have been in contact with them ever since and has not had ONE response to the cancellation request, regardless of various emails I sent. I received a threatening sms with regards to the debit order that I reversed in April, requesting me to contact them by phone or by email address they provided. I cannot get through to them on the number provided (tells you to go to the website) so I opted to email them to the address provided. NO RESPONSE. I then received an e-mail from Elsabe Labuschagne requesting me to contact her. Same result as before. I then faxed her on the number provided. That was yesterday. NO RESPONSE. I reversed the next debit order this morning as well! WHAT HAS ONE TO DO TO GET THIS CANCELLED. Even when you have followed all the rules and have all the proof!