Trying to be a model really involves trying more than once. Mailing agencies should be the goal of an aspiring model. Many girls want to be models but what separate those who book modeling jobs and those who just "call themselves models" has to do with submissions, trying again and not giving up if there is no response the first time around.
It takes many to get working with an agency, and it can also take a model's own hands-on effort to book her own experience in front of the camera, building her portfolio and really knowing how to market her self with the right photos, and learning from observing her own photos on what she needs to improve on.
It is rare to submit once or twice to an agency and get a call back. You might have to work for months or a year before you hear back. So beware of the real work it takes.
Improving and trying are a constant action within the pursuits of being a model.