Formal — to staff
Vending · Machine
You
すみません、この自動販売機にお金を入れすぎたようなのですが、返却ボタンが見つかりません。
すみません、このじどうはんばいきにおかねをいれすぎたようなのですが、へんきゃくボタンがみつかりません。
Excuse me, it seems I put too much money into this vending machine, but I can't find the change/return button.
Romaji: Sumimasen, kono jidōhanbaiki ni okane o iresugita yō na no desu ga, henkyaku botan ga mitsukarimasen. / Reply Romaji: Achira ni arimasu yo. Kono botan de henkin saremasu.
Reply
あちらにありますよ。このボタンで返金されます。
あちらにありますよ。このボタンでへんきんされます。
It's over there. This button will refund your money.
Gesture & etiquette
Point to the vending machine, make a searching gesture around the coin slot.
Some older vending machines might have less obvious return buttons. If no one is around, look carefully for a small button, often labeled '返却' (henkyaku) or with an arrow pointing to coins. If you can't find it, consider buying something small to get change. Do not shake or hit the machine.