No, you are not obligated to retain the immigration services offered through E-JAM. It is advisable to use such a service because of their expertise and knowledge in immigration matters. They provide representation services for applicants before the Canadian Embassy, i.e. preparation of application forms and all supporting documentation; follow up, when necessary, with Citizenship and Immigration Canada officials regarding the status of application; assistance and advice in preparation for interview with visa officials (should an interview be necessary) and answer any questions an applicant may have regarding her/his visa application.
Please note that it is not the responsibility of E-JAM, or your prospective employer to process your immigration application; it is your responsibility. E-JAM’s experience is that using such a service increases the chance of obtaining a work permit.