Without contacts in the business it would be nearly impossible to successfully promote yourself. Once you know what you are doing you can decide if you are satisfied with your agency, or if you want to go to another one, or promote yourself. It is much easier for women to promote themselves enough to work steadily because they do a lot of promotional work, such as car shows, boat shows, store openings, etc. If you do a good job the first time, it is likely that they will hire you back whenever the need models in the area again. Ideally, an agency will find work for you, as well as providing any career advice you may need.
Some agencies just have so many models that the personal guidance aspect is lost.
YOU have to take charge of your own career. Don't expect them to call you no matter what they say. If you haven't heard from them in a few weeks, call. They can do this best by advancing your career. In return for finding you work, the agency gets a portion of your income from each job you do.