How to correct suite number listed for my service address?

The online sign-up for Comcast Business doesn't accept my suite number though it lists some other suites in my building. I called customer service about this and they said not to worry, go ahead with the online sign-up and I'd be able to change/correct the suite number during the process.  So I did, however, I haven't been able to find any way of changing the suite number in my service address, and I have an installation scheduled for later this week.  I tried calling customer service again, and this time I was told that the previous person was wrong and there's no way to change my service address other than closing my account and then calling to have a salesperson setup a new account.  The problem with that is I can't get the same internet service offer through a phone order and the price difference is substantial.

Can someone please simply correct my suite number?  One of the sellilng points for my lease was the building manager assuring me that getting Comcast service would be no problem as the entire office building is wired for Comcast and other occupants' suites have service.  

Any and all help is greatly appreciated!