depending on how big the agency is sometimes you have to show the agency you have been busy for them to stay interested. Even if it is something as simple as getting a new compcard or headshot made or adding a new great portfolio shot to your portfolio and letting them know you have been active.
Gettin booked once or twice in this day an age doesn't mean your modelin agency will call you constantly you still have to show them with your effort that you are serious, and busy and ambitious and until you build your portfolio you might have better luck freelancing with many modeling agencies than just one.
Agencies are a marketing tool. So just because you have one interested in working with you, doesn't mean you should sit on your butt and wait for them to call. Still stay busy!
This day and age, it is about self serving and being very active within your pursuits.