German phrase
Über welchen ~ wurde gebucht?
Meaning
Through which ___ was the booking made?
When to use it
Asks which booking source. It is formal and clear, often referring to a tour operator or agency.
Example dialogue
Über welchen Veranstalter wurde gebucht?
Through which tour operator was the booking made?
Wir haben bei einem deutschen Veranstalter gebucht.
We booked through a German tour operator.