No response to query

I am a Discovery Vitality member. Membership no11 ********** 1. Unfortunately I don't use any of the Vitality benefits and want to cancel my membership to Vitality. This seems impossible as you can only reach Vitality by phone and every time I phone I am told that someone will come back to me and I am given a reference number, the latest ref number is ********** 4420. This has been going on for 2 months. I am at a lost how to get Vitality to respond. Thank you Johan Beneke