Damro Furniture Pvt Ltd — Office Chair defect and no service even with guarantee

We bought an office chair from Damro, Gachibowli 4 months back. It had 1 year guarantee with it. 1 month back, a screw came out from back support. We called Damro, asking it to repair, they have been ignoring our calls from past 3 weeks now telling that they will be sending a person next day. Now 2 days back I got reply that, i need to pay for the service and parts, even when i have the bills, guarantee card everything. I really need to get it repaired asap.