How do I know if this guy at the store was flirting with me?

Ok so I went to an electronics store the other day to replace my cell phone charger than had broken the other day. I had this warranty thing where I could just replace it. First off, the employee there asked my age in a jokingly way. Then we began to talk more while we waited for the warranty to go through. We talked more and it was very easy to talk to each other. We even play fought over my driver's license and touched each others hand. In all we talked about 20 minutes. He also mentioned something about buying a cell phone but he was joking, and I quickly told him that I wasn't interested in buying one. Later on before I left, he gave me the store business card and wrote his number down saying, "Call me if you need anything."