too much responsibility….discount room sales cashier

I been working in retail as a sales clerk for a few years. I meet all the requirements for being a great sales lady that customers like returning to me because they know im going to provide them with Top of the line service.

I am consided a floater in my store, it means I go around and take care of covering peoples lunch breaks,and covering thier departments when people decide to call in sick,or whatever. I come in to work sometimes on my days off, I work overtime when they need me to. I work really hard and managment completely walks all over me and takes advantage of me. Well,Im pissed because of this Discount Sale room they have in the department store.

When i first started working in the store a few years ago, there was 2 cash registers open -that is how it should be, because that room is busy around the holidays.

Well this year, they decided to only put 1 Cash register in the room, and Managment Depends on ME. To do everything by myself, and sometimes take care of lines of customers that go on atleast an hour or so. At the same time, the phone is ringing, and other customers are asking me to do price checks. And i understand that customers dont like waiting in long lines around the holidays, But obviously, Management doesnt. And Christmas is coming up soon, The Busy-est time of the year, And its up to me to take care of this discount room by myself with no help..
And another thing,, I been working in the same place for 3 Years, every year they come up with a new excuse not to give me a raise. I only make $7.50/hr, That is the same amount I was hired on a few yrs ago, They have kept me so long there, i must be doing something right,, Is that right?? Why wont they give me a raise? Well this yr, they wouldnt give me a raise because accidently left a sensor tag on a piece of clothing. Its just so stupid. I know I am short of finishing my college degree, and I need to do that soon so i can hopefully get a better job that pays more. Do they really think I will work there every yr for the rest of my life, and not get a raise? That is exactly why I feel that I am being used, and taken advantage of at the work place. Its just wrong what they are doing to me.