Bad / uncaring service from GEMS

It is now for months that I am battling with GEMS to get part of my chronic medication. Every months since December 2020 they do not have the medication, then if you threaten them they quickly find some and the next month they do not have it in stock again. One months I could get it at local pharmacy and had to pay an extensive levy. How can GEMS not have this medication for months, whilst every other pharmacy has it in stock. We need to find a solution for this ongoing problem as they just do not care.