Can you cancel the orange sim only contract at any time?

There a various types of SIM Only contracts with various lengths and cancellation periods. The most common one is a 30 day SIM Only contract. A 30 day SIM Only contract can be canceled with a 30 days notice. Further details can be found here http://www.simonlycontractdeals.co.uk/sim-only-deals.html. Scroll down to where it explains "30 day contract". Hope you find it useful.