Airtel — outgoing not working while on roaming

My airtel number [protected] having a prepaid recharge of rs. 349 on 9th september with facilities o[censored]nlimited local and std calls and 1gb 3g/4g data with 28 days validity upto 7th october 2017. However, the facility of local or std calls are not working while i landed in kolkata. All outgoing calls gets disconnected in a second even before ringtone is being heard.
This is really disturbing as i used to make number of calls everyday owing to my business and just after landing in the airport, i am unable to ring and contact anybody, i find myself in a helpless situation. Does this mean that airtel is an unreliable service provider. As nowhere it was indicated that roaming to a different city in included or not included in the plan.
Moreover, when i dialled 121 or 198, it was mere fun and mockery since it only asks to dial all numbers in the number pad except helping me to talk to any responsible guy and tends to promote different sales plan without addressing the problem.
I don't know if this complain really brings sense to the business leaders of airtell to think how really they can help customer instead of showing colourful advertisements.