Airtel Postpaid - Refund Issues

I'm Airtel customer since ** years, and i have my complete family is airtel. I'm suffering that my phone internet isn't working properly and it's been *.* years, and i'm complaining continuously but they are not resolving my complaint and after making a call to customer care they will said that your complaint is been closed, but my internet issues remain same.

It's been a long time they are doing the same thing continuously with me, without letting inform to their customer they closed their complaint.

Because I'm facing internet issues, i bought a new router device on (*th Dec, **) from Airtel with * month's advance subscription to do my work in flow, I'm again regretting that why i bought it. That fucking devise is also working slow.

I call again to customer care to refund my ****/- as i have bought it from Airtel store. Now they are saying, we can not refund your as it is advance amount.

I'm seriously fedup with there pathetic services, I need my refund back from Airtel.

Date: ** Dec, **. Please help me in this matter.