Discovery refusing to acknowledge wish to cancel medical aid.

After numerous attempts to cancel my Mum's medical aid as we have immigrated to the UK, they keep making the excuse that the email "differs from the one we have on record for you" Yet this is the email address that we receive communication from them. They used exactly the same excuse when I tried to cancel my medical.

I believe these are delay tactics to avoid cancellations. Is anyone else having this issue?