Momentum policy cancellation

I have requested to cancel my Myriad policy with them and the process is absolutely ridiculous. When I took the policy I worked there and the email linked to it was my work one. I'm now being told that in order to cancel the policy I need to send the instruction from that email address? How when I no longer work there and therefore have no access to it? I have notified them of this and they still insist on it. If this is how they treat a former employee just imagine the process for normal clients.