Can I end a contract for poor performance on other party's part?

Two years ago our family entered into a service contract with a college consulting service for our son who's going to university next year. We are unsatisfied with the service thus far, primarily for the quality of essays produced and unwillingness of service provider to answer questions and provide us with updates on the progress. Of the 14 schools we intend to apply to, 4 applications have been processed. Consulting service has performed some of contract but still has services outstanding that we no longer wish to receive. Contract stipulated final payment on 11/1/15, with consulting services to continue until April 2016. We would like to end the contract but consulting service has intimated legal action against us. We have already paid 80% of the total $3400. Contract has no cancellation language.