Don’t worry that I have shown a lot of corrections to your letter. The letter was well thought out, concise, was clear in what you meant and was above the minimum word count (essential in the IELTS Test). The errors are mainly to do with using the correct prepositions, not starting a sentence with ‘But‘, use ‘but‘ only as a linking word in the middle of a sentence. There were also a couple of verb tense errors.
You also needed to sign your letter Yours Faithfully. If you had used a person’s name such as Mr Brown you would sign off Yours Sincerely. It is important to use these in the IELTS Test.
You used standard phrases that are good to use in a letter but needed to be worded correctly. Here are the correct ways to write the following phrases you used and you can now use them correctly in future letters:
I am writing this letter to inform you….
…this is not the first incident like this to happen….
…do what is needed…. OR …do what is required…
…I will inform the……
You used some very good words and phrases such as: recently located, incident, unfortunately, not suitable, sincerely request, look into this matter, as soon as possible. These are all excellent to use in a formal/business letter in the IELTS test.
See my feedback below. The first document (Edited Version) has the editing marks so that you can try and correct your work yourself. The second document (Corrected Version) is the corrected version so that you can see the corrections I have suggested.