need advise on advertisement contract

Hi my name is victoria, work as office manager in medical office. got by fax americanhealthdirectory.com online advertisement contract, didn't read it carefully i thought it insurance asking to confirm doctor's information, did sing it and dated, in few weeks got invoice for 2 years agreement and fee of $500 per year. Faxed over notice asking to cancel it explained that misunderstood it. Now a guy sending me faxes asking me how much can i pay, promising to wave 2nd year fee, he is not giving me phone # to call, i have know idea if he even belong to the company and much more question. Asking him via fax questions and # to call because i have no idea how is that web site working and so far, so on, he is not giving it out and giving me an attitude via fax. gave me a discound to 350 (to pay in 3 months) and giving me few days to pay first 150. stating that will make a police report. Can i do something about it? I am not even sure he is working for that company. Cannot find enough info.