Airtel — sim is out of coverage and airtel support and outlet not able to fix this

My sisters' number is of mp/cg circle. When she came to bangalore 3 weeks back, sim went to out of network coverage. We contacted customer support 2 times but didn't receive any help as they just said it will be working within few days. Then we visited to airtel outlet which is in itpl, bangalore on 25th july, they have given another sim and said it will be working within 4 hrs but it didn't started working after one day so again i visited there and there said sorry, now it will be activated in 4 hrs and now today it's 29th july, neither old sim working nor the new sim get activated and when again i visited the same outlet they said number not get activated bcoz of father's name mismatch and also they told that someone might have typed it by mistake and now it will take another 7 working days if i would provide them some docs.

So what's is our fault here? Which kind of service airtel started providing?
We got fed up with this worst service