The employee who perform their termination of work contract. Discussing a termination of employment by mutual agreement means that your employees will feel more respected. Another option is to have the employment contract reviewed by an experienced employment lawyer to determine if the termination clause is enforceable. Trust me, then you can sue for compensation for the number of days the notice did not cover.
The agency provides resources to employers, you may be able to negotiate terms of the contract in order to persuade the other party to allow you to end it early without negative consequences.