A Formal Letter
Dear Mr. Adams -*
I´m {I am} writing You to express my dissatisfation with the hotel service. I and Tonight, my family and I** went*** tonight to our room and it was a mess. It wasn´t {was not} clean and it was disorderly. I had said {better=indicated, mentioned} by telephone that we would need an additional bed, but it wasn´t {was not} there. We had to get to another hotel. SoTherefore, I demand that to return our money be returned {better "refunded"} because we didn´t {did not} sleep in this room.
Yours faithfully.
In business correspondence, we avoid using contractions as much as possible because it sounds informal, so it's better to say "I am", "it was", "was not", etc.
*"Dear" somes across as a bit informal for a business email or letter. We usually just say the person's name, or write "To whom it may concern"
**In English, we normally reference ourselves last.
***I think you mean "checked into our room" here, i.e., it was the first time you saw your hotel room.
A formal letter
Dear Mr. Adams.
I am writing to you to express my dissatisfation with the hotel service. When my family and I checked into our room tonight, it was a mess. It was not clean and was untidy. I had explained by telephone that we needed an additional bed, but it was not there. We had to go to another hotel, so, I am requesting that you return our money because we did not sleep/stay in this room.
Yours faithfully.
Avoid contractions isn't, wasn't, etc.) in formal writing. :>)
A formal letter
Dear Sr.(Mr.?) Adams,
I´m writing (to you)[not needed] to express my dissatisfation with the hotel service. My family and I ("I", "We" always at the end. E.g., He and I went to the fair.) went to our room tonight [last night... tonight usually indicates the night that is yet to come], and it was a mess. It wasn´t clean (avoid negatives. Use: was unclean) and disorderly. I [mentioned on - better phrase] telephone that we would need an additional bed, but it wasn´t here(better: provided). We had to find another hotel. So (better: In this light / In view of this incident), I demand that you refund our money [ because we didn´t sleep in your room - redundant, not needed]
Yours faithfully.
