Medshield not willing to reimburse member back.

In September we had to pay for my oxygen machine out of our own pocket as we had difficulty getting it approved. We paid the first month and delivery cost, it was then approved. I have been trying to claim this amount back since then. They keep giving excuses, I don’t know what to do anymore. First I was told the documents aren’t clear, I managed to get an account statement with payment from the service department, I then submitted. Then they said I had to submit to another department. Now there is a code wrong.