SIM card that belongs to other person name but I bought and ricarded im now look

I bought a phone at MRP store last year September and have been using the phone since 14 April lost a phone the I went to the responsible store as I took an insurance with them they needed an ITC ref I had to call responsible network provider only to find out that the SIM I bought and left the shop with it's not under my name but belongs to someone's name so I could not get help as I'm not the lawful owner of that SIM.Mrp personnel are not being helpful in this matter as to how did I get the SIM card that doesn't belong to Ricard at their by the cashier whom was helping me please assist me cause now I'm looking like a stupid in front of everyone