Airtel — Airtel sim card is not showing any network.

I am working in Dubai. I visit India once in a year. I have been using one Airtel sim. But suddenly my Airtel sim is not connecting to any network in Dubai. All the time it showing "Emergency call". The same thing happened before also and I changed my Sim when I visited India last month. It was working fine till yesterday. But now it's not working at all. I will visit India next year and all my account is linked with this Airtel no. How am I suppose to work with all those accounts. Please solve this issue.