Xfinity is not giving back the proper amount after cancelation (Scam???)

I had a one year contract at $75 a month, after the year was up i noticed that they charged me $125 a month prompting me to cancel.
My prior balance was $0 as they charge a month ahead of time. They charged me the new month at $125 so my account should have a negative balance of $125 up until the new cycle starts.
My billing cycle was from mm/20/yy to mm/19/yy. I canceled on Dec 09, meaning i had 10 days left in the current billing cycle and had not yet started the next billing cycle. With a current negative balance of $125 i would expect the refund they give me to be $125 ( the amount that i never should have been charged for anyways since i canceled before that month started) PLUS whatever i would get back since i only used a portion of the current billing cycle (Nov 20-Dec 19th)
HOWEVER, what they actually sent me in the mail is a statement saying im only getting back $44, how is this possible you might ask, since at a bare minimum it should be $125 since that's money they shouldn't have taken in the first place. On the statement it says the following, "On your last bill you were billed in advance for services between Dec 20 - Jan 19. We've applied a credit of -$167.99 as a result of your service dissconnection on Dec 09." This sounds all well and good and $167.99 is reasonable seeing as $125 of is was charged to me when it shouldn't have been, however on the next page it says that my current account balance is $125.....
They are still trying to charge me for the month that i got charged for in advance even though i canceled before that billing period even started. $125 balance with a $167.99 credit leaves me with $44. 
What makes it even worse is that on the statement it says you can only dispute for a certain period of time, so if i didn't notice this them xfinity would have just stolen the $125 from me and most likely would not give it back even upon prompting due to the "you cant dispute after x days".