If you bought the phone under contract and have satisfied that contract, Orange should be able to provide you with an unlock code. There are also a few legitimate reasons to request an unlock code before the contract is up, including travelling abroad outside Orange's network, but it's really up to their discretion whether or not they provide you the code.
There are some sites that claim to be able to provide unlock codes for a fee, but I personally don't trust them and unlocking a phone doesn't relieve you from any contractual obligations. It just let's you use the phone on another network.