Cheaper internet access

I've been a Comcast customer for almost 18 months and I've generally been happy with the service.  I know that DSL is cheaper, but as I don't have a land line it's not really an option.  I've heard that many people have gotten deals from Comcast by calling them and saying they are thinking of getting DSL.  I gave it a try this morning; I told them I'd been getting ads from Verizon about how cheap DSL was.  I now have cable internet access for $19.99 a month for the next three months.