Melita review: Deposit 1

Hello,
I went to Malta on August 29, and wanted to have an Internet connection. There were 2 companies to connect Internet, but it was obligatory to choose Melita, because my home owner was using Melita. They connected the Internet and took € 75 deposit for modem from me. I was leaving Malta on November 18. I called Melita, and asked that how can I get my deposit back. They said that, “You have to come one day before your flight, and we will give your deposit back.” I went to Melita on November 17, one day before my flight, and gave their modem. Then they said that “We’re going to give you a cheque and you will be able to get your deposit in any HSBC bank in Malta in five days.” I said “Are you serious? I’m going to leave Malta tomorrow.” Then they said, “it is our procedure.” (bytheway, it was not written anywhere). Then I filled a bank transfer form to get my deposit to my bank account, with about € 20 administration fee and they said “You’re going to get it in 5 days.” But it’s 12th day, and they haven’t sent the money, and furthermore they don’t respond my mails. What can I do now? I think, I can do nothing...