《投诉信》A letter of complaint用英语怎么写?

Dear Sir:
With reference to our order No.W 98,the 120 computer sets supplies to the above order were delivered the day before yesterday,but we regret that 20 sets were badly damaged.
The packages containing the computer sets appeared to be in good condition and we accepted and signed for them without question.We unpacked the computer sets with care and can only assume that damage must be due to careless handling at some stage prior to packing.
We shall be glad if you will replace all 20 sets as soon as possible.Meanwhile,we have put the damaged computer sets aside in case you need them to support a claim on your suppliers for compensation.
Yours sincerely,