You're estimating what, that every customer would on average spend at at least an hour a month on the phone with each and every service they do business with?
There is a reason that most companies make it hard to talk to a human before you've already exhausted all other support channels.
Make something like that a right and people will use it. Maybe 99% of the time you won't need a human for a particular service in a month, but there will be users who are on the phone every day, maybe multiple times per day.
And your monthly fee would need to exist to pay for the users who abuse the right.