Tata Indicom — Not responding for disconnecting

Sir,
I have taken a data card from Tata Indicom for internet. Till from the date of connection i am not getting speed. For the same i have complained to the Tata indicom center & told him for disconnect my connection & give me my deposite amount back.

They replied that we will send our engineer he will solve the problem. Engineer came but then also the problem will not sort out. He told me that within two days we will disconnect the same.

But now more than 10 days over what can i do?