Siti Broadband — Security Deposit not returning

I have taken a connection from Siti Broadband. While connection time they said that Rs. 2300/- is security deposit and will be returned while surrendering the connection and modem. But now they are refusing and saying it was activation charges.
Now a days every service provider is providing free connection and modem so I am not so fool that I will pay this hefty amount to new comer in the market. Even their services are worst. Once it went for one week and after that they corrected the issues.
I think like this Siti Broad have cheated a lot of people in the market. Be careful while taking connection. thehttps://www.https://www.consumercomplaints.in/new_complaint/ are completely fraude.