Send copy of cancelled invoice together with Order cancelled email

[Johan Boshoff]

Good day.

I have customers that are very unhappy when a pending upgrade order was cancelled (due to not paying before the next due date for the service) and they are not informed that the invoice was also cancelled and then they pay the cancelled invoice etc.

To sort out this problem, I need a hook once a Pending Upgrade Order email gets sent to the customers.  I just need to include the cancelled invoice to this email. 

Please let me know soonest.