Unprofessional

I caught myself in hospital early January and my medical aid did not cover some costs incurred. As a result I had to pay for the shortfall and got two invoices from two different suppliers which I paid in full without fail

Fast forward to 13/05/2021, I get a call from Lancet notifying me about my overdue account. What surprises me is that I had never received any invoice from Lancet prior to the call pertaining to the overdue account spoken of. No invoice either via email or post whatsoever. It is really shocking to get a call alerting me of an overdue account I know nothing of. How do I get handed over to a debt collection company if you never even bothered to send me any invoices. I'm utterly disappointed and confused that you would only alert me months later