Shaw billing when closing account

In the last few months I've closed two Shaw internet accounts (business and personal). In each case I paid the final month's bill and returned the equipment to a Shaw outlet in person on the final day and got a signed receipt. In both cases Shaw sent me a bill weeks later still showing the equipment outstanding, and then they proceeded to dun me with automated phone calls and letters threatening to turn it over to Collections if I didn't pay up. How can they not know that the equipment has been returned when it was entered into their computer on the spot to print the receipt? When I called them, they said to just ignore it, their system is slow processing returns. Excuse me, but this is both inefficient and unprofessional. Shaw should smarten up and fix this.