I had TV and Internet. Called and cancelled TV in the end of Sept. Around the middle of Nov I called to add TV back, and had a date of install for like Dec 5th. I called in like Dec 27th and said I needed to cancel the install. So retention got on the phone with some department that came back to me with the deal of 55 etc etc.
I did this all via the phone, and I just made it seem like I was only getting it for the Lakers that I didn't really need it. So they were trying as hard as they could to keep that install.
I think you can make it work if you just be extremely polite and just be normal. Have a conversation with them, and just let them walk you into a price. If you don't like the price balk and say it won't work for you, etc.
And with ATT you can always call in and ask for promos. HBO Showtime promos, upgrade tier for 6months promo. Upgrade internet tiers. Im getting 18mbs a month for 37, I know that deal can be beat, but for ATT its pretty damn good.