Airtel Prepaid — disrespect of a primary customer(girl)

The incident happened in airtel gallery which is located in ghatkopar east. I was der and one of my cousin had a broken sim card which she wanted to replace it and she was asked to get the documents, which she had brought along wth her but an executive(seemed a junior) talked to her rudely and asked her to get other documents which was not required for a new sim. Then a senior also joined him, who has an award presented by airtel for some achievement which is on the wall of the gallery, and he also seemed to be the senior but didnt have the sense to talk to a girl and i joined the arguement as she was a cousin but der was no proper response or guilt in both of them for talking in an unethical manner. They also rejected the change of sim card, whereas the requirements and documents were all present there with the girl. Just because of the rift and maybe the ego they rejected to give her a new sim card.
I would like to know what should i do to take proper action against them.
I owe two airtel cards, a prepaid and a pospaid(which was mentioned to them). So they should be consider me and my cousin as their primary customer.
Please take action against them or suggest me some way.