Dear Mr/Ms/Mrs (Surname)
Gent. Signor/Signora (surname)
I am writing to you in regards to your email
Le scrivo in merito alla Sua email
We deeply apologise for any inconvenience
Le porgo le nostre più sincere scuse per i disagi
I understand that your vacation was not what you hoped for.
Capisco che la vostra vacanza non sia stata come speravate.
On behalf of the agency (name), we apologise for the inconvenience
A nome dell’Agenzia (nome), le porgo le nostre scuse per il disagio
In regards to the issue with…
Riguardo alla questione di…
We are sorry that the room was bad
Ci dispiace che la camera era scadente