We got a 'bundle deal' a year ago after we moved into our new house. It was $175 a month, including phone, internet, cable, multiple HD DVRs, HBO, Starz. I just got our bill this month and it was $263! The year was up. So I just called, said I was concerned about it going up so much, nicely mentioned that another company was in our area and was there any new deal I was eligible for? My bill is now $153 a month...same exact services, etc.
I would first call and ask. If that doesn't get you what you want, say thanks anyway and hang up.
Then look for ads from the 'other guys' with better deals then you're getting. Call back and, nicely, say that you got this offer and are considering switching to save X amount of money per month and can they match that? You can also ask for their retention department specifically...those people often have more power to make decisions.
Be super, super nice. People want to help nice people. And if you get a canky rep, tell them you're getting another call and will call back and hang up and try again later.
Good luck!