Making an airtime top-up comes in handy for different applications - personal and businesslike. Reloadly's Airtime API handles these use cases by providing endpoints that grant you access to over 700 operators in more than 140 countries.
With this outreach, you can send airtime and also subscribe to data bundles in different currencies. The most important data you will need to send airtime successfully is the recipient's mobile number.
To further learn how to integrate this RESTful API into your application, you can check out this documentation. It contains a reference of each endpoint in the Airtime API.