In Stebby, the Service Providers can choose whether or not they wish to offer the option to purchase the Service from Stebby beforehand. If the Service Provider has enabled the option to purchase, the "buy ticket" button will also be displayed next to the Service.
If the Service does not have this button and instead there is a letter indicating that the Ticket is not pre-purchase, then it is possible to pay for the Service only at the Service Provider's point of sale. At the service provider's, you must present an identity document and express a wish to purchase the service. Be sure to mention that you'd like to pay for the funds in your Stebby account.