The contract was written very good for them and very bad for me. When I asked for some things to be changed, I was completely ignored.
I may have misunderstood you here but if you asked to change something in a contract that had already been signed you can't really expect too much sympathy from any agency, or from me.
You get the contractual details sorted before you sign anything. If the details are not to your liking, don't sign it. Simple as that. And if your requests for changes of contract details are reasonable I bet most agencies today will do their outmost to meet your requests. Thats my experience from negotiating contracts at least.