AT&T You Guys Aren't Going to Believe THIS!! Internet

On 11/16/12, I changed my family plan to an individual plan and reduced the phones on my plan from 3 to 1.  Since AT&T bills and requests payment in advance, I would have thought that the reduction in my service and devices would warrant at least a partial refund on the November bill...BUT NO!!  AT&T changed my cancellation date (on their own) to 11/27/12 (which happens to be the billing date of my account) and decided that there will be NO proration of my bill. 

I've been an AT&T customer for 10 years.  I've paid their exorbitant rates and dealt with their anal contracts.  I've always defended them when I heard about them jacking up other people.  Usually, when I call in and speak to someone, I'm able to get some kind of adjustment, but in this case no matter who I talk to, I'm getting the run around.  

How on earth can I reduce the devices and service on my plan and yet deserve NO refund on the bill that they require to be paid in advance??  How can I call in to change services and reduce devices and have AT&T DECIDE for me when the changes will actually become effective?  If I had added more devices and extended my plan DURING THE BILLING CYCLE, would I receive a proration increasing the bill??   

AT&T has apparently gotten so very big that they are able to bully and cheat people and get away with it.  Since the iPhone isn't the premier phone that it once was, it might be time for me to change providers.  I'm officially looking for a better deal with their competition....