First Clarity Senior Java Developer interview questions

They contacted me for the first time but then I haven't heard from them for almost 3 weeks!!! so I decided to contact them again and they arranged the interview. Everything went very well with the interview itself and they were very happy with that and they gave me a job offer and contract. The problem started when I wanted to apply for my visa because I was outside UK! I needed a code called "Certificate of Sponsorship" but they guy who works there gave me a wrong code and my visa application has been rejected and costed me 922 Euros but when I spoke with them about the problem they didn't accept its responsibility and they didn't refund any thing!!! First they didn't answer my emails and calls for one week and all my contacts also didn't work.