International roaming

After subscribing to IR service for USA from Airtel, I'm unable to connect to AT &T anywhere in USA.  It says AT & T forbidden, unable to connect.  Trying to mail airtel every day several times, but they say the email is not registered with them, but how come i receive my airtel bills to that email address?  They ask me to authenticate the email, but how can I authenticate if don't receive service and hence no OTP.  Complained on Twitter also, not even a response, let alone resolution.