Airtel — Sim registration failed 2g to 4g

Address:

Bhadrak

While upgrading my sim number 2g to 4g my sim registration has failed and no tower is coming.When I contacted the shop he told me that the sim belongs to other name you cannot take it with that old number .But I was using this sim aleast 10yrs before at that time the sim was given without any documentation and we have no idea that which name the shop had given for identifying the sim .Now I want the old number of that sim to be restored..