Flipkart - Received defective Onida microwave Oven from Flipkart

I have ordered Onida ** L Air Fryer convention microwave oven from Flipkart on **th May **** and it was delivered on **th of May ( Order ID: OD******************) , they scheduled demo on **rd May but cancelled it before the schedule (**nd of May) and I have tried to bake cake with the help of user manual but the heat distribution is not proper and it was burnt on top and not baked in the middle and bottom also I tried its special feature Air Fry with potato slices but it not even cooked **% , hence I have raised return request on **nd of May and return request was accepted from Flipkart on **th of May (Return ID ******************** ) , They scheduled return pickup on **th of June and gave assurance that it will be picked up and refund will be credited in ** days after pickup, but they took * months by sending mail updates saying due to lock-down pickup is delayed rest assured we will pickup the product , frequently I followed up with customer care more than ** times but they just registered the complaint and closed it by marking resolved without any resolution or update, by believing there fake promises I waited * months for them to resolve but they Cancelled the return request on **st July stating the return window is already closed . But I have raised return request within * days which was within return window, When I contacted them again they registered the complaint as usual and still they are updating like they are closely working with vendor to solve the issue and this will not happen again but I have wasted my **** + Rs on useless defective product by believing Flipkart , they don't care for customers trust and they have return policy for customers but why don't they have policy with vendors .? I am customer to Flipkart they are forgetting that and acting like I ordered it from Onida directly. I have lost all hope from Flipkart by waiting from * months , Please help me to fix this issue .