Unhappy customer

My Vitality premium is outstanding and I received an sms saying that I should call to make an arrangement by 09/05/21. I called Discovery on the 7th and was transferred to the finance department, spoke to a guy by the name of Davian and made an arrangement to pay on the 20th May. He assured me that I have nothing to worry about and that they wont cancel. To my surprise they have just cancelled my membership and I've had to spend 20 minutes on the phone trying to sort it out. Why sms me to make an arrangement and when I do try make an arrangement get told that I have nothing to worry about, only for you to cancel my membership just like that?