Despite the strata management contract terms, most strata managers will be open to voluntarily terminating the agreement early. You may need to negotiate a payout of part of the base fee for the period foregone. You might need to give notice, often 3 months, but that can be overridden if both parties agree to do so.
Also, many strata management agency agreements are invalid, due to recent changes to the strata law, especially because of the insurance provisions in the agreement. So if a strata manager digs their heels in, take the agreement you signed to a strata lawyer for an opinion of its validity. They can also negotiate the early termination of the agreement.