NOT RIGHT!!

There are two options when cancelling.

One is a standard cancellation, where your service is terminated at the end of the current service month, which is already paid for.

The other is an immediate cancellation, which terminates the service that day, and for which there is a prorated refund, which is for the remainder of the service month that was already paid for. HOWEVER, this must be requested by the subscriber at the time that the cancellation is requested. If this is not requested, it will be a standard cancellation.

If you did not request an immediate cancellation, the service will still be technically "on" for the remainder of the service month, even though you no longer have the equipment connected. If this is the case, this is why they are not refunding the remaining of the service month. 

For reference, this is a typical practice of companies that use forward billing for service (paying for the service month you're about to start rather than one you just finished), such as HughesNet, DirecTV, Dish Network, etc.