Non-payment of doula services AFTER Discovery confirmed that they will pay

My wife and I had our first baby in Feb 2019. What a happy moment... :)

Prior to the delivery we requested authorisation from Discovery Health for the delivery. We also wanted to use a doula's services (doula = birth companion), so I emailed Discovery to see if I need authorisation for this too. This was their response: Ref no ********** 216

"The services of a doula will be paid from your Medical Savings Account, as long as you have funds available. Once you have given birth, they will submit the claim and we will process it. No authorisation is needed for the doula as there will already be your child birth authorisation on system."

We paid the amount due to the doula and submitted a claim for reimbur*****t from our medical savings. Discovery now reviewed the claim twice and did not pay it for the following reasons:

"We have not paid this claim because there has not been an authorisation for this service in the past four months".

I am NOT trying to claim this amount from the hospital cover (i.e. the medical aid fund). I am merely trying to get a reimbur*****t from MY savings account.