No service

Hi I am currently in US Chicago and  I have an airtel postpaid number and international roaming is activated but All I see is no service.  I’m paying the bill Every month just to retain the number for bank transactions. I have had multiple calls with customer care but they have not been able to resolve this issue and the only thing I get t hear is in 24 hours this will be resolved which does not happen and I do not even get a follow up on this. I have changed the SIM card to multiple handsets. Tried resetting the network settings and it still doesn’t work.