Asking Someone to Repeat That

You didn't catch what someone said and ask them to say it again.

Clerk
Son treinta y cinco mil pesos.
sohn TRAYN-tah ee SEEN-koh meel PEH-sohs.
That's thirty-five thousand pesos.
In Colombia and Chile, prices are often in thousands. Don't panic — 35,000 pesos might only be about $8 USD.
You
Perdón, no escuché bien. ¿Puede repetir, por favor?
pehr-DOHN, noh ehs-koo-CHEH byehn. PWEH-deh rreh-peh-TEER, por fah-VOR?
Sorry, I didn't hear well. Can you repeat that, please?
'No escuché' (I didn't hear) is softer than 'no entendí' (I didn't understand) and feels more polite.
Clerk
Treinta y cinco mil pesos.
TRAYN-tah ee SEEN-koh meel PEH-sohs.
Thirty-five thousand pesos.
You
¿Cómo dijo? ¿Treinta y cinco?
KOH-moh DEE-hoh? TRAYN-tah ee SEEN-koh?
What did you say? Thirty-five?
'¿Cómo dijo?' is a polite way to say 'What did you say?' using the formal 'usted' form.