Airtel — my airtel sim is not working in usa

Address:

Chennai, Tamil Nadu, 600049

My number is not working in the usa for anything sms, incoming and outgoing. Please let me know how to get it activated. My number is valid and was bought less than 6 months and brought to usa with the intent o[censored]sing in international roaming for incoming and outgoing calls and messages. It says sim is not provisioned. It used to work initially when i came to the us. Recharge is also returned and not successful.

Thanks,
Dinesh