Airtel — refund for broadband connection, that was not installed, has not been received

I applied for a connection on 2nd dec and paid rs 500. The airtel dealer first said that it'll take rs500 to install connection, then a month later, he said that since it's fiber cable, total rs1000 will be installation charges. So i made the second transaction of rs 500 on 18 jan.

I have since sent them my bank statements and transaction ids. But still they were saying that it's invalid.
Also, they are asking me to go to my bank ask for charge back. Indian banks don't provide chargeback.

Why take money before providing connection?