You are correct: if they presented the contract to you (rather than you to them, or it being mutually negotiated between you and them) then by them presenting the contract to you, they made an offer (and showed their consent to the terms they came up with); when you accepted that offer (by signing) you created a binding contract. You and they together could voluntarily choose to cancel the contract and replace it with a new one, but you'd have to consent or agree to do that; otherwise, you can enforce the existing contract for its full length or duration.