Question has been asked before but never really aswered.
For personal and professional reasons, I cannot afford my $249 (!!!) plan anymore.
I cannot change/cancel my plan online MYSELF. I get the usual:
" We're sorry, it looks like you'll need some help completing your order.
I'm sure you noticed, but the ability to manage your own plan isn't working well. It's a known issue: http://forums.xfinity.com/t5/Customer-Service/Can-t-manage-your-account-online-Getting-an-error/m-p/...
That said, since Comcast doesn't allow on line downgrades or cancellations, you'd still need to call to accomplish what you want. Alternatively, one of the Comcast employees may stop in and offer to help. Good luck.