Unable To get proper registration status in fresh Airtel Sim card in SIM800A

I was using airtel sim cards in my smart metering application using SIM800A. everything was working fine but suddenly I have started facing a strange problem. The sim cards that I use show me the status of registration as registration denied. I have some SIM900A modems as well. If I use the sim cards first in SIM900A modems, it works fine in it. Also after using it in SIM900A firstly, it works fine later in SIM800A based modems. The same SIM800A based modem works fine for other providers sim cards

I have faced this problem with some Airtel SIM cards. But new ones seem to be working fine.
The one that didnt work on my SIM800C was a SIM card written 64K. I am also not sure if that it is the problem. But you can contact Airtel to clarify the IMEI registration denial. May be the IMEI number is blacklisted in their server.

Thanks, Ravi. By IMEI registration denial, You mean when the for the first time, the sim card tries to establish the connection with network with IMEI of module, it won’t work as the IMEI number can be blacklisted at provider’s end but it will work thereafter as the first time registration process of the sim card is completed with IMEI number of the module (Possibly SIM900A or a cell phone) which is not blacklisted ?

For me that sim never worked in GSM modules. Don’t know why exactly. May be that SIM was not meant for use in M2M devices. Its still a mystery to me. I used different Vodafone SIM cards and moved on.