Questions & Answers about Una vez que terminé, llamé.
Una vez que means once or once that / after in the sense of as soon as something has happened.
In this sentence, Una vez que terminé, llamé means Once I finished, I called.
It introduces a clause that sets up the first action:
- Una vez que terminé = once I finished
Then the main clause gives the next action:
- llamé = I called
It is a very common way to connect two actions in time.