The Numbers page lists every service and country that has numbers in stock at that moment, more than 150 countries in all. Stock changes through the day: a country that is out now may have numbers again later.
A service that is not in the list can still be verified: pick Not Listed / Other / Any as the service. A number bought that way receives the SMS of almost any sender. It usually costs more than a number bought for a named service.
Numbers receive SMS only. They cannot make or take calls, and they cannot send messages. Verification for banks and other financial services (payment apps such as PayPal, Cash App or Venmo included), crypto exchanges, government websites, identity verification services and mobile carriers is not supported, under “Not Listed” as well.