Here is a basic example conversation you can use if you need to call your school or supervisor.

Office Person: Moshi moshi/ Ohayou gozaimasu. SCHOOL NAME/DEPARTMENT desu.

Hello/ Good morning/ This is SCHOOL NAME/DEPARTMENT.

You: Moshi moshi/ Ohayou gozaimasu. YOUR NAME to moushimasu. PERSON wa irasshaimasu ka.

Hello/ Good morning. This is YOUR NAME. Is PERSON there?

Office Person: Hai, chotto matte kudasai/ Shoushou omachi kudasai.

Sure hold a moment please.

If they are there, they will transfer you. But if not:

Office Person: Omatase shimashita/ Moushi wake arimasen ga…

Thank you for waiting/ I’m sorry but...

Office Person: Shucchou desu/ Jugyouchuu desu/ Kaigichuu desu.

They’re out of the office/ in class/ in a meeting.

You: Hai, wakarimashita

Oh, I see.

You: Hoka no eigo no sensei wa irashaimasu deshou ka.

Are there any English teachers there?

You: Soshitara, YOUR NAME ga denwa shita koto wo tsute-ete itadakemasen ka.

Can you tell them I called?

You: Dengon wo yoroshii deshou ka. Message…

Can I leave a message? Message…

You: Yoroshiku onegaishimasu. Sore dewa, shitsurei shimasu.

Thank you, have a good day.