Roanna, I don't know of a way to turn the immobiliser off, but your dealer has fobbed you off, they should have used their diagnostic equipment to locate the
problem. I'd have looked at the immobiliser reading coil, fitted around the ignition lock, at first.
Do you have two keys, and if so do they both have the same
problem? This would tell you if it's a car or a key
problem.
Are you sure it's the immobiliser?
Leon7284, what exactly have you lost???