Is www.flug.de Safe?

Please stay away from this site. I booked and paid for two flight tickets using Sofort payment system but I never received them. Instead, the next day I received an email from flug.de that the tickets would cost more and if I didn't pay they would cancel the tickets. I opted to cancel the tickets and sent them and email and called their customer telephone number. They said they would refund the money but more than four weeks have passed by and I haven"t received my money. They have not answer my emails and now they have not answer their customer telephone either. At least from Frankfurt I have tried different numbers but not success. Only an automated system that tells me I am in position one for hours! First time I write a review in wot but I have to say this and warn you.