Discovery Medical aid

Good day. I have been a member of Discovery Medical aid for the last 30 years. On the 4th November, I submitted 3 x invoices which I have paid, and requested that they re-work them and refund me, as I have been put onto the oncology scheme, and the invoices are cancer related. To date I have not been refunded, although I keep getting told that they are busy with it, but have system problems. I have had numerous reference numbers either on email, or verbally.