I can't take this stupid case off my iphone?

It's a cheep plastic case and I tried to decorate it but ruined it so now I want to take it off but I can't! It's an iPhone 5 and Its annoying:/ how can I take it off!

Cutters, clippers, brake the edge off 1st with small precision screw drivers…

If one can't see the case you're on about, not much advice can be given really!