No network in USA

I arrived in USA on 1 April 2019. Since then there is no network on my airtel sim. I called up the customer care from another number, they asked me to activate international roaming. I therefore recharged my number with 400+ rs worth of international roaming pack. Today 3 weeks later, there is still no network. When I call the customer care, they refuse to help. Airtel number - 9646879575