To be checked - please help!!!

Hi,
Is there any chance that someone can check is the below complaint is correct? I would appreciate, if you could help me. It's realy important for me. Thanks in advance.

Dear Sir/Madame,
On xxx, I booked tickets for flight No. XX1 (from... to...for 28th of December) and flight No YY2 (from... to... for 31st of December) on your website. I didn't realise that the ticket for the XX1 flight has been booked twice, until I checked-in and printed boarding passes. Everything seemed to be fine for me - 2 flights, 2 reservations, 2 e-mail confirmations - so I didn't check the details and simply checked-in.
As far as I can remember there was a technical issue during the booking process: after I entered my credit card details and pressed the continue button an error occurred, so I started booking once again. I am obviously not going to use both of these tickets and I can assure you that it was not my intention to have 2 tickets for the same flight. If I got the confirmation of the reservation screen after I first time booked the ticket, I would never started booking procedure again. On the other hand - why would I buy 2 tickets for the same flight?
I realise that I am partially responsible for this situation. On the other hand however: shouldn't your booking system be improved so that check-in would not be possible to be done twice for this same ID?
I have flown with XXX few times before and I have always been truly satisfied with provided services.
I look forward to hearing from you and to a resolution of this problem. Please contact me at the above e-mail address.
Yours sincerely