Airtel — airtel: [protected] showing "no service"

Address:

530018

I have been using airtel no: [protected] since five years.in the same phone elephone p8000 in other sim slot bsnl is working. But suddenly from 06.02.2018 showing "no service". Also i tried in other xiaomi mi5. But still the sim is showing no service. It gently requested to resolve the issue and give me the explanation of why it happening though there is still balance amount in account.