She is booked up all next week.

I regret that a previous engagement prevents me from accepting your kind invitation.

I'm sorry, but I have a previous appointment for tomorrow.

If I had not had a previous engagement, I could have come to the party.

I have a previous appointment.

I'm sorry, but I have a prior engagement.

I'm sorry I have a previous appointment.

Do you have any previous appointments next Sunday?

I already have something planned for Friday, so I won't be able to make it to the drinking session.

I'm sorry. I have another appointment.

I have a previous engagement at ten.

Tom had a previous engagement.