Another bate and swith, Comcast told me that:
"There's no cost to update your equipment, plus we'll waive shipping and handling fees for your Self-Install Kit. "
After talking to comcast to order new modem, I gave verbal authorization that confirmed no costs and continued subcription at same rate.
After they sent me the new modem, Comcast refused to ativiate it unless I authorized a rental fee that I never paid in the past.
I guess you should be happy that you got a free rental for however many months. Not really a "bait and switch" though, just a billing snafu in your favor.