You should get some kind of appraisal during the year, which is where you can put accross what work you have done and how you feel that the work you do now isn't reflected in the pay you receive.
If you don't get an appraisal, why not ask for a meeting to discuss your job. Im not sure if after a year you should get one, but some jobs do offer a yearly evaluation, or go up with inflation!
If you're doing more than what you should be or your job has been given more duties, then it's worth asking for!