Documentation not pulling through as it should

I have canceled a value added service within the 14 day period where they stated it will be canceled and yet they still want to bill me for it and a month ago I filled in a banking details change form and sent it through and now it seems that they still haven't loaded the correct banking details which is affecting my credit score in a very bad way so I am very disappointed in the service I received during this year alone as usually I don't get bad service.