Air tel has deactivated my prepaid mobile connection service

I am using this prepaid connection for the last 10 years.i  had purchased this number with life time validity plan.it has a validity up-to 2030.i had registered this number for all my banking  services. Airtel has dis-connected my connection on 8th September 2015 .when i contacted the airtel customer care the guy told me that the service was disconnected for document verification,so he asked me to submit my documents in any one of their air tel gallery.so as per his instruction i visited the air-tel gallery in saidapet the name of  the gallery is saidai telecommunication in chennai at (12th September 2015),the executive in the showroom told me that the sim was allotted to another customer ,i was shocked and he asked me to contact the nodal team.when i contacted the nodal team they told me that the sim was assigned  to another customer.when i ask for the reason they told me that the sim was  automatically disconnected for  not making any incoming/outing calls.but unfortunately i am not in India for last 3 months and my  mobile was in international roaming that why i don't make any calls,but it was  inserted on my mobile and i received incoming messages everyday for my banking and other services,without my knowledge they deactivated my sim and allotted it to another customer.they don't give me any proper intimation before the  disconnection.when i asked them for re-connection they told me that it was allocated to someone.As per the telecom consumer protection six amendment act of 2013 the service provider need to give 15 days of grace time for service re-connection,but air-tel has failed to providing me of  those  grace period.i sent numerous  emails regarding about this issue but air-tel appellate is not giving any solution they are repeating the same for me.is there any possibility to take action against airtel,DId i have any possibilty to get back number.

 

Reference Number for Contacting Air-tel Appellate =QZUBR11006716666