Receptionist job

So I took a receptionist job a few weeks ago and have been trained in and have been working. Every week so far my boss is adding more thing for me to be doing. The issue I'm having is its all cleaning duties. I'm getting paid $12.00 an hour. My job does mention cleaning as part of my role but legit the job should have been listed as a cleaner. That is all I am doing with very little anything else. It's absolutely exhausting 3.5 hours worth of work. I never leave on time and I only get paid for 3.5 hours of work. I desperately need this job so I don't feel like I have wiggle room. What do I do?