Airtel — two sim card with same mobile number

Address:

New Delhi, Delhi, 110045

Please be informed that i have purchased a sim card on my wife name from ak communication, mahavir enclave, new delhi on 21.04.2018. As informed by shopkeeper it will be activated in 30 minutes, i have saved the airtel number to check it's activation and found that the number is already activated to other person.
When checked with customer care it was found that sim is already activated since 08.04.2018 with other name.
It is requested to investigate the issue, how two sim card of same mobile number can be available for sale in market by airtel. It's a case of cheating with customer. Please find the details of sim card below:
Sim card no.[protected]u.
Mobile no.[protected]
Regards