The experience you get in doing this will make you more attractive to future employers. Take pride in that and don't for a minute think about asking for a rise. If someone did that to me in first week of employment they wouldn't make it to the second week. Any reasonable employer will see how you are doing after a few weeks and if you are being paid inappropriately would adjust it. Wait a month and if you think the responsibility you have is not reflected in wage THEN discuss, but not yet. Peoples satisfaction at work depends on bosses being reasonable, flexible, appreciative, communicating well and so on. Wait until you have the measure of all of that before acting.