insurance company rejected my claim

I had raised a claim for theft of my phone and I was told by the insurance company that 6500 rupees would be reimbursed into my bank account.For reimbursing the amount, they asked for an FIR copy with the signature of the sub inspector, Stamp of the police station and IMEI number of the phone, which the police is denying to give. According to the police, FIR is booked only for theft mobile phones which cost more than 50,000 rs. Instead the police had given me a certificate of theft with the signature of the sub inspector, Stamp of the police station and IMEI number of the phone. They said that it would suffice for claiming the insurance amount. I have provided them that certificate and they have rejected my claim and are denying to reimburse the amount without a valid FIR and the police is not booking an FIR.
The insurance company has given me a really tough time. Their customer service is also very poor. Contacting them was very difficult. Whenever I called them, they told they would get back to me with the concerned department but they never did. They have no sense of responsibility! I am a student and I was having my exams at that time. They misguided me and wasted my time and energy. I would like to sue them for mental agony.
My Claim ID – OC-20-9915-6615-00006671 under Complete Mobile Protection Plan with Policy ID – JPPOFFK1315698