Question - Finding an error in a paragraph

Hi. I have a question. There is an error in the paragraph below(ones that are underlined). I can see that the answer is “consider extremely unprofessional”, however I wonder if there is anything else is also wrong(such as (1)?)

Thanks in advance.

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I wrote to you on May 100th, 2006, (1)explaining that the merchandise I ordered from you (2)hadn’t arrived. I am attatching a copy of that letter for your convenience. Having recieved neither the merchandise (3)nor a reply to my earlier letter, I am asking you to refund my my money. I have attatched details of my bank account. I (4)consider extremely unprofessional that your company failed to deliver the goods and (5)also failed to respond to my complaint.