I (as an individual) have signed a contract for services (with a company) that runs for 12 weeks. I have just given the required four weeks' written notice of termination. The company's representative has told me that the notice period does not start until the end of the initial 12 weeks. I am sure (and have said) that that is unreasonable and unenforceable as it would effectively turn a 12-week contract into a 16-week one.
I'd appreciate someone with knowledge of contract law confirming that my reading of it is correct.