I’m sure it is a case by case decision. And as with you, Comcast isn’t known for their discounting; at least over a long-haul relationship. They may give initial discounts to draw business, but those soon drop.
Our cable provider where we live is Cox Communications.
I also recently dumped my landline we did have with Cox, in favor of a VOIP service (T-Mobile @ Home) I added on to our T-Mobile cell service for an additional $10 per month, which includes long distance. It works well.
It was simple to set-up. I just plugged our existing set of cordless phonesets (which are placed throughout the house) into the router T-Mo provided and nothing in practical usage changed ... except of course, the price. We save something over $20 per month by the change, depending on what our long distance bill might have been with the cable landline.
We also put our entire T-Mo bill in my wife’s name so we get an additional 12% discount off the total, corporate discount, due to the hospital where she works. Cox isn’t offering any corporate discount, I might add. I wish T-Mobile would offer broadband internet!