Account paid but 1 year later receive invoice?

I received an invoice for services rendered to my dad last year on 23/07/2015.This account was paid by the medical aid on the 17/10/2014 according to their records.This invoice is strange in that it reflects a charge for<br> rental on the 31/10/2014...yet my dad passed away on 25/06/2014?Goods were delivered to us on the 19th of june 2014 and collected on the 28th of june 2014 by your rep.<br> <br> Why am I receiving a invoice now?account no ***7.