Discovery Health won't refund my claim, they sent a cheque of which they have no details!

I took my daughter to orthodontist on 12th June 2018 and they accepted cash payments which can later be claimed from medical aid. I submitted my claim on the 14th June to Discovery Health. Days late I called in to confirm they said they did not have my bank details and they sent...wait for it... a CHEQUE to the address they have on the system. And they used Post Office. Okay, I updated my bank details, and they said they will cancel the cheque and deposit the refund into my bank account, but only after they have the cheque number. Today I called to ask the status some clueless lady told me they still don't know the cheque number they've sent. I asked how can they send a cheque of which they don't know details she said their system works differently and that the cheque must be recalled from post office and come to back to them. Its weeks now waiting for my refund