¡Hola,
buenas
tardes!
Tengo
una
reservación
a
nombre
de...
OH-lah, BWEH-nahs TAR-dehs! TEHN-goh OO-nah reh-ser-vah-SYOHN ah NOHM-breh deh...
Hi, good afternoon! I have a reservation under the name of...
"Buenas tardes" is used roughly from noon until sunset. It works both as a greeting and a farewell.