You can only get out of the contract if:1) The contractor breaches (or violates) the terms of the contract in some material (or important)  way, such as can't do the work when promised (if there's a date in the contract); can't provide the siding ordered; tries to charge you more than is *in* the agreement (even if there were initial discussions about a cheaper rate, for this purpose, it's what's in the contract itself that matters); etc.2) The contractor committed fraud to get you to sign up with him: he misrepresented (lied about) some material (important) fact, which misrepresentation caused you to enter into the transaction, and it was reasonable for you to rely on the misrepresentation (i.e. no warning signs or reasons to doubt). Otherwise, in the absence of breach or fraud, you would be locked into the contract.