Lancet/Dischem incompetence

We had a covid test done at Dischem in June. Everyone in the country knows that you cannot have the test done without upfront payment. Since June lancet have been demanding payment from us. No matter how many times we send them proof that we have paid and explain you have to pay upfront. They have now told us Dischem owe them 3 million rand and haven’t allocated all the payments. Yet we still get demands to pay on a daily basis. Surely this is a lancet/Dischem issue and not ours. Their incompetence and inability to do a basic job is beyond me. How can you sort out an issue with people who don’t understand what to do. Any ideas on how to sort this out will be welcome!