I think there's a mistake in the bill.
KREH-do — stress on first syllable. 'errore' = air-ROH-reh, three syllables, stress on second.
Use politely when you spot a discrepancy on the bill. The subjunctive 'sia' after 'credo che' softens the accusation — you're suggesting a possible error rather than accusing.
'Credo che ci sia' uses the present subjunctive: 'credo che' (I think that) triggers the subjunctive mood 'sia' (there be). This is grammatically correct and more polite than the indicative 'c'è'. It softens the claim.
C'è un errore nel conto.
There's an error in the bill.
More direct, less subjunctive — still polite.
Questo non l'abbiamo ordinato.
We didn't order this.
Specific challenge to an item on the bill.
Il totale non torna.
The total doesn't add up.
When the math seems wrong.
Billing errors in Italian restaurants are not uncommon, especially in tourist areas. Always check your bill ('conto') carefully. Common issues include charging for water or bread ('pane e coperto') that wasn't consumed, or double-charging for an item.