Learn Spanish (Latin America): El recepcionista con quien hablé sugirió el hotel. - The receptionist with whom I spoke suggested the hotel.

Sugerir (to suggest) is an "-ir" verb that has a stem change in the present tense. In the preterite (past tense), these "-ir" verbs have a special rule: the "e" in the stem changes to "i", but only in the third-person forms (he/she/it/you formal, and they/you all). Since the receptionist is a "he", we use the third-person singular form sugirió.

I thought stem-changing verbs didn't change in the preterite tense. Am I remembering that wrong?

You are half right! For "-ar" and "-er" verbs (like pensar or volver), there are no stem changes in the preterite. But "-ir" verbs are the exception. If an "-ir" verb has a stem change in the present, it will also have a small stem change (e -> i, or o -> u) in the third-person forms of the preterite, which is why we see sugirió here.

Why is it el recepcionista? Doesn't the "-a" at the end mean it should be feminine?

Words for professions that end in -ista (like recepcionista, dentista, artista) can be either masculine or feminine. The ending stays exactly the same regardless of who you are talking about, so we use the article to show the gender. El recepcionista means a male receptionist, and la recepcionista would mean a female receptionist.

Why do we use quien here instead of que for "who" or "whom"?