I cannot speak for how any other dealer would handle a cancellation process, but from a functional standpoint in Alarm.com for the dealer it couldn’t be simpler. They simply need to delete the Alarm.com account. The module is then available for registration with another dealer as long as it is 4G.
In some cases users have had trouble, yes, it depends on the dealer and the circumstance of their contract usually.
Please be sure to reference the guide regarding 4G vs 3G modules:
Once your service is cancelled you can check registration status and get started at the page below!