تحفظا in English:

I've got a reservation.

Will the fare change if I change the reservation?

How early do I have to make a reservation to qualify for the discount?

We deliberated whether we should cancel the reservation.

You don't necessarily have to go to the airport to reconfirm your plane reservation.

Unfortunately, I don't have a reservation. Do you still have a double room available?

I have a reservation, my name is Kaori Yoshikawa. Here's my confirmation card.

Please tell the reservation clerk, Mr Ichiro Takahashi, your credit card number to confirm your reservation.

Please wait a moment. Yes, we have a reservation for you.

He also phones the rest-house to make sure that the reservation has been confirmed.

I can't get you a reservation just then; is later OK?

Definition if you make a reservation, you ask a hotel to keep a room for you, a restaurant to keep a table for you, etc.

To be honest, I have strong reservations about the project.

a Navaho Indian from a North American reservation

He had some reservations but eventually I convinced him.