Ampath Credit still outstanding!

I received notification from Ampath of a refund owed from 2017. Filled in the forms and was advised that the money would be paid. It's been 3 weeks and I have followed up by mail and phone. The staff don't even listen, they put you through to an agent that never answers. My credit is still outstanding! Yet they are very quick to make calls if they even think you owe them a cent!