Airtel — network busy every time

Address:

Thane, Maharashtra, 400615

I am facing issue like network busy and unable to call. It is so irritated because of continuously having.
Whenever i am trying to connect someone.
1. Mostly first time get connected. But in case next person is busy or not get connected. And next i will try to connect, it is unable to get connected. Message throughout network is busy. Then if want to connect again then i have to wait for 10 to 15 min.
2. Once i have done first call. Unable get connected second call. Same message as above.

Mobile no. [protected] this is postpaid connection. So in that case i have to pay whole amount.