Sorry that all they hired you for was on-call. That means that you are not on the schedule even part time. You have to wait around for a phone call to work, usually when somebody calls in sick at the last minute or does not show up for work for any reason. It is not much better than not having a job at all. You really should continue your job search
. But, you might get to work a lot, if a lot of people call off a lot of the time. Still, you want a set schedule like everyone else. So continue looking. That is my advice. Good luck and congrats on the job. Hopefully it turns into a part time, then a full time job if you can't find something else.