I'm not sure how to break this to you, but you have the phone inserted in the case upside down!
Try it the other way round and make sure that it slips into the sides of the case and all the way down. You may find that all is well then.
Please let us know.
Edit 1: Actually, I take that back having looked at the photos more carefully and having seen the orientation of the vaja logo on the back. I thought at first that this was a Vaja iVolution Top SP, the same as I ordered , which has the fastening on the top rather than the bottom. I'm off to their website to see which model yours is.
Edit 2: Well I can't find that model on the website. What is it?