You might want to try. I am sure an Internet only is still cheaper than Double Play/Triple play. I would disconnect or schedule a disconnect and just see if they offer a cheaper plan to get you back. If not, you can always reconnect after one month.
3 years ago, with TWC, I canceled the TV portion. TWC retention called me up before my scheduled disconnect day and dropped the rated by $25.
With my parents, couple of years ago, I switched them from Verizon DSL/DirecTV to FIOS. DirecTV called me up and offer to drop TV portion price from $54.99 to $24.99. I told them thanks, but no thanks, I want my parents to have faster Internet since they watch streaming chinese TV.
So, you might threaten to cancel and see. Of course, YMMV. As mentioned, you can always reconnect later.
Just a little disclaimer, I live in NYC. There's some competition going on here, depend on the neighborhood and building, you may have some combination of choices in DirecTV/Fios/TWC/RCN/DSL. Might be the reason the rate can be negotiated easier.