I am a recently qualified corporate assistant and I am disillusioned by the lack of responsibility and client care I get. Should I quit, or should I stick it out?

Have you made your concerns known to the partners in your department? Firms need to keep their assistants happy, so it is definitely worth asking for better work/ more responsibility before you start looking around. It is also useful to take stock and decide what you want out of your career on an ongoing basis. Once you have a list of the things you want from a job, you can start looking at your options in law or another field entirely.