comcast cable communicatons 'BAIT AND SWITCH' denver, Colorado

this is my second problematic situation with comcast.  in this instance i went to a office site and ordered comcast high speed internet, as advertised on television, for $19.99 per month for 12 months.  i was then told that i'd pay a $3.00 monthly fee for the use of a modem, provided to me by comcast.  there was no installation fee or other charges involved.  all this happened on september 17, '09.  before months end i'd gotten a bill from comcast, due 10-02-09, for $73.00!!  wow!!!  the explanation comcast has given to me has miserably failed to account for this charge.  the next month, october, i got a bill for $50.00.  in less than two months comcast was billing me in excess of $120.00 for a $19.00 per month promotional.  because i already had basic cable from comcast, for 9.99 per month, and since i'd filed a complaint with the local bbb claiming comcast was double billing me and extending bill payments upon me, i requested of comcast that they separate my two services so as to enable me to discern what i am being charged for, whether it's for the basic cable service or the hsi service.  comcast wrote the bbb that they (comcast) considered the matter closed.  this is the arrogance and disrespect that this company has.  a few yrs. ago i'd ordered another promotional, this one for 6 months.  however, when the service didn't work correctly and comcast had to make about 4 trips to my house, and another several 'trips' over the phone, and the service yet was unfulfilled and, worse, the package i'd signed up for was changing, had changed and in some instances was gone altogether, i told comcast that i wasn't going to continue paying them what our agreement had spelled out since they hadn't kept on providing me with the programs and services the contract called upon them so to do.  again, comcast just ignored the facts and insisted that i make payments to them for the full amount of the advertised promotional, even though it had changed, much for the worse.  to this day, comcast has some collection agency bothering me every so often, and it's on my credit report!!  at present time both myself and the bbb are awainting a response from comcast onthe initial complaint, as the latter one is old news for me (i'll never p ay them a single dime for this account!!)  now, though, comcast has pulled their "bait and switch" move, by claiming that their promotional from september, when i signed on, is either 29.99 or 39.00 per month, and, worse, that it's only for 6 months, not a years as advertised when i got it.  we all need to stand against these businesses by letting them know we will fight them tooth and nail!!!