Pro Techno — they are fraud

Same happened with me... They are telling me to pay the amount of 4100/-... I know i have not done so many mistakes... And i have a proof that there is no mistakes in some of the forms... But still they added it in a mistake list... Now one advocate named chetan sharma... Mailed me telling me to pay them a money... Or they will take legal actions on me... I don't know what to do... I m in fear... Please help me out... Should i pay them or not??