International Roaming does NOT work!

I bought a monthly Rs. 3999 international roaming pack from Airtel for use in the USA, prior to departing India. Its now been 7 days since I arrived in the US, and my phone continues to display "no service"! I've tried everything on the device, to no avail. The Airtel geniuses do not list a call center phone number to call.

Does anyone have any suggestions on how to solve this? I've emailed Airtel but am not holding my breath waiting for a response from them.

Thanks,
Guru