said by Jon J:... increase to the rate you were told it would?
Maybe because they don't tell you what that non-promo rate is going to be? ISPs are very bad about a) not telling customers what the "standard" rate is, and/or b) hiding it in obscure fine print, or hard to find web pages, making it difficult to find.
While switching ISPs to get that dirt cheap rate can be messy, be glad you even have that option.