Cheatd by Wireless phone agent

Last year, I signed up a one year AT&T wireless plan via Yi-Tong, an sale agent in Flushing, NY. I swiched to another vendor one year later, still via the same agent. But AT&T wireless is now charging me early termination fine (about $350) since their record shows this is a two year contract. I never signed such a two year contract with AT&T Wireless. The only contract I signed with Yi-Tong, the angent, was a one-year plan. They might used the signature and credit information that I provided and made up a contract with AT&T. I called AT&T and told them the situation. They said I have to deal with the agent. But it's hard to get in touch with the agnent now( tried to call them, never got through). My questions are: 1. Can I claim that Yi-Tong made a fraudulent contract with AT&T Wireless by forging my signature and ID info? 2. If answer 1 is yes, can I just reject the fine w/o dealing with Yi-Tong, cause they are hard to reach? Any advice is highly appreciated!