There is a very well known restaurant in Iran’s Chalus Road, which has a valid 5-digit phone number, but on Google Maps the digit (0) is not placed before the area code, which triggers “the called number is not valid” response over the phone (if called directly from Google Maps).
I attempted to edit the number, but here’s the result:
In order to increase error checking, in each country the phone numbers that are supported are just those that are of the standard length for that country. “Short code” phone numbers are not supported.
Short codes get redirected to a full phone number, if you can find that number out you can add it to the feature.
