Airtel Bharti Company - Sim not working

I am using airtel no which are registered with my mother's name. *th February, **** suddenly my phone shows emergency network, I thought that may be it's network problem but after ** hours when I visit to near by airtel office, they told me that my sim is not working and need to be changed. I want to know the reason then they told me it's often happened. Then I applied for new sim for that no and give them my mother's aadhar card for verification. But they are not accepted my mother's aadhar card because as per their concern supreme Court declare that aadhar card is invalid for sim registration. Then they ask for voter card and then I am given them my mother's voter card, but there was little problem in name, in voter card it is 'i' instead of 'y'. Now they playing game with me. They told me that I can't take new sim before correction of my mother's voter card and they are not taken any other id proof for verification. There is only one way left, it is portability of this no from my mother's name to my name and as per airtel offers I can't port in prepaid. Now tell me, what is my fault. I am unemployed. I can't afford postpaid and I am using this no for last ** years,so you can understand the importance of this sim. I can't withdrawal money through atm. I am helpless.