refund mistake

I added a new member to my medical aid in Feb 2015 to be active in march 2015. Cancelled my medical aid in march so the last payment was for the end of march .a payment went off in April so a refund was due of R 2880.I got an email saying an amount of R 4000 plus and another R 530 for vitality was to be refunded.I called because that was to much and I never had vitality.I was then told I owed them for the month of January and Feb because my application to add a member had a start date of 01/12/2014 which was put on in error. So when i sent the application through to be processed in feb,how did the consultant not pick up that he/she is processing a date that has passed already and why would the system allow back dating applications? This makes no sense why anyone would apply to be covered for months that has passed.However discovery has advised I am liable to pay for January and February because the application dated Dec 2014 but application was processed in February to be affective 1 march 2015. Needless to say I am under the impression we still sorting the issue out but this morning I only received a refund of R530.??? I think this is just plain incompetence. I want my money back