French phrase
J'ai réservé à l'avance.
Meaning
I booked in advance.
When to use it
States that arrangements were made ahead of time. It is calm and factual, often used to avoid travel problems.
Example dialogue
Le train de dix heures est complet, vous avez une réservation ?
The ten o'clock train is full. Do you have a reservation?
J'ai réservé à l'avance. Je voudrais confirmer mon siège.
I booked in advance. I would like to confirm my seat.