Reliance Trends — Not removing tag

Address:

10/7 Rishabh nagar durg cg, Durg, Chhattisgarh

I am a regular customer of reliance trends. I bought some cloths about two months back. Exact date not remembered. In one shirt the store forgot to remove magnetic tag.
When I reached the store today, they are insisting for bill or purchase date. Why should I face trouble for their fault. Now the shirt with tag is of no use to me.
Rishabh jain
Sr Divisional Accounts Officer