I had SBC/Yahoo DSL for $27/mo. The way they did it was to bill me $49/mo or something like that, with a "promotional credit". After a year, my bill suddenly jumped -- the rate didn't "change", but that promo credit went away.
So I called up and asked what I had to do to get the promo rate for another year. I couldn't, they said -- that promotion was for new customers only, and only if they signed up online.
So, I went online and signed up as a "new" customer on my second phone line :-) Got the promo rate for another year, and as soon as it was up and running I canceled the old one. I only had one month without the promo discount. Of course the new account included a starter kit with a set of filters, new Cisco router, etc. Since I already had all that stuff I sold the second kit on eBay for almost $100.
This year they were a bit smarter: They sent me an email that basically said "Click here to extend for a year at your existing rate" and so I did that. I suppose I could have "churned" again, back to the first line, and gotten another starter kit to sell on eBay ...
Gordon S. Hlavenka