Invoiced for called Account

I have cancelled my account with Nester to in May for both my vehicles but to my surprise I am getting invoices that I must I called I was told that they are invistigating after 2 weeks I called as well they were not getting back to me the lady at retantion department said it shows that I cancelled but now I'm still getting the invoice what is happening isn't this sorted you cannot be ****ing people like this