Tata Sky — again asking for charge for new box

iam H khan co. Id. [protected] purchased multi connection ..first was normal box they supplied and installed but when screen was unable to show channels properly boy went away and charge was deducted 1800 rs ...after repeatedly complaining to tata sky toll free no. just next day they told ki aapki tv me nahi chalega doosra (higher version) purchase kariye when i asked ki nahi chalne wala tha ye to pehle kyo nahi bataya ...ladka jo lagane aya tha usne bhi nahi bataya ...they told me ki hum kuch nahi kar sakte doosra purhase kariye when i asked ki replace kar djiye and ill pay the difference they said we cant help you now after paying 1800+200 wire charge etc iam unable to see channels and iam feeling black mailing that i have no option kindly help thanks and regards [protected] [protected]