Mate, shame on you if that is your best reply. A bit of ranting at people live there longer than yourself and have been through it for business and personal matters. So much for being subject matter expert.
LOL. No need to beat around the bush: agents targeted here are mostly the ones using tea money and sr. relationships to use back doors.
The agents used by businesses help you sort your papers but require the same effort except for the visits to officials that are streamlined. And often mentioned as (too) expensive.
Sorry, but there are multiple people here stating the system shows greyed out boxes. There is only one conclusion: clearly the system is still broken. Probably the same old sage they did not test it for popular browsers. As a user there is zero need to do stuff you suggest.
Which honestly is another design flaw. Not required then don't show it, or make it work correctly. And that includes being able to empty the field, not answering.
Do you have a google (gmail) account? Then just use Google Voice. You get a real phone number that your US based contacts can call, you'll receive their call on your mobile. And you can call them from the app (for free). Note; you might need a US-phone number to receive an 'activation code' for google voice.