Cancel Account form not accepting account number

Need to cancel account ASAP as we are rolling out of promotion period and leaving office.  Surprised to find the 30 day delay in cancelling account....they can start you immediately but need 30 days notice to disconnect.....don't understand that.

Anyway, need to fill out the form asap so I don't get another month super high pricing.  No one is available to take call and when I found the form to fill out to start the cancellation it won't accept my account number.  I have copied and pasted straight from my account.  By the time they get back in office, I'll probably have to pay another month of service at a location I won't be at.  Any help figuring out the "ethernet" account number would be helpful.