Unprofessional Accounts Department

I've just received a bill from November 2016. According to melomed I'm owing them. I was shocked!!! 2016. They say there was insufficient funds on our medical aid. My problem is, why has melomed waited so long to inform us. They had all our contact details and address. On the same address and cellphone number they had for us in 2***, they've now posted a letter and sms'd us of this outstanding bill. What the he'll is wrong with they're accounts department, it's a total mess. If we knew we didn't have funds we would've paid this amount in 2016. This is utter nonsense!!!