I'm having the same problem and settings/support/usage manual not helpful.
I understand that the form will revert to whatever is in the General Settings if left blank but there are no instructions about what to put in the form's "Email From Name:" field to NOT make it revert to the general settings and instead use the custom "name" field I created. Even something to make it use the senders email addy instead would be better than "Custom Contact Forms". The instructions are very specific about what happens when "Email From Name:" is left blank but frustratingly absent of any other directions.
Seems like an integral and basic part of any contact form.