Airtel — international roaming to usa not working

Hi, international roaming is not working in usa. The number is active for more than a year.in june 2017 the service was suspended and reactivated in july 2017. This is a post paid number, (My plan-199 - mh). When called, customer support asked to send email however no response to the email. Also, no effective answer from tech support team. The escalation process is not effective, i never got call back from them. It is frustrating that even after requested to escalate to sme to resolve the issue, there is no proper response.