Service tax due for fy 2014-2015 emai

Got an email  for  Non Payment of Service Tax/ Central Excise duty on the earned income for the FY 2014-15. I work as an IT Consultant for a USA firm. I work  remotely and get paid in Dollars(which gets converted into Indian currency). I  do not have any service tax number, as I was in the impression I am not eligible to pay the tax as my  client is not in India. My income is more than  threshold exemption limit of Rs. 10 lakhs . Kindly guide me how should I go ahead with it.