Asking for more money at interview

Ok so I have a in person interview coming up for a job repairing and moving semi trailers and on the phone they asked me some questions. One of them was how much do I want to make an hour well I wasn't thinking and just quickly said a low answer the guy on the phone seemed surprised by how low my answer was and I knew I messed up. I have skills they need for the job and a CDL A as well. How do I ask for more money at the job with our looking greedy or messing up the interview?