English to Spanish Bus/Financial International Org/Dev/Coop microsavings

"Have loaded airtime credit at a supermarket till"


It's a list of action taken in a text about mobile phone payments and those sorts of things -so this is all the context I have. They just mean putting credit into your phone through a message sent to your phone when you requested it (at a 7 eleven for example). I'm pretty sure we do not use the "airtime" idea in Spanish, but wonder if there is a more formal way of saying this than "poner crédito en el celular". Chas gracias.