Changing approved Chronic Medication

My mother is a 80 year old lady with a long list of chronic medication. We go and collect the medication form Clicks Ben Fleur as it is one of the preferred suppliers for discovery medical. We have approved medication that is approved with discovery. Twice we have been to collect the medication form this pharmacy that they change the medication with other medicine that is not on the approved list and then we have to pay in hundreds of rand that cannot be afford by my mother as he only receives a small pension and from that still pay for her medical aid. When we bring it under the attention of the pharmacist they say it is because they do not have stock. This scrip was handed in by them of the 6 months and now they never have the stock. If we ask for copies of the scrip to take our business to another pharmacist they say they must first go and get it out of the filing. This is the second time that this happen and when you phone them to complaint the phone never gets answered. We rely on a service as discovery wants us to use clicks as an provider then we get service like this. All I want is copies of my prescriptions so that I can take my business elsewhere.