A receptionist connection is prepaid, then reserved
The reserved line is paid for before the slot is withheld.
Adding a concurrent inbound connection now charges a full month at purchase, whatever day of the billing period it falls on, and the connection is not reserved until that charge succeeds.
Why it works that way. A connection is not a feature flag. It is a slot withheld from every other claim on the fleet from the instant it is granted, busy or idle, so granting one ahead of payment gives away the scarce thing the price exists to ration. The charge is a full month rather than a fraction for the same reason: the reserve itself is not scaled to the days left in the period, so a fraction would price less than the platform actually gave up.
What you are told before you agree. The confirmation step states the exact amount and the exact date your subscription next renews, because a connection bought shortly before a renewal pays its prepaid month and then renews. That is disclosed rather than smoothed away.
Your existing lines are untouched. A connection you already hold keeps the dunning grace it has always had, so a receptionist you already pay for keeps answering while a payment retries. And if a new purchase fails on your own card, your connection count, your billing items and your line’s admission all stay exactly as they were.