Swiggy Instamart Grocery - Some items not delivered inspite of paying for the whole thing

I had ordered a lot of items from swiggy Instamart on *th March ****. There were * bags. But I got only few of the items that is only * bag. Almost half of the items were missing. I complained and told them that I did not get all the items that I have ordered and I have paid the full amount. They told me that they cannot do anything about it so u email them your problem and assured me that once I email them they'll be able to solve my problem. I emailed them but through email too they said the same thing that they won't be able to help me. I then called the delivery boy and I told him I had ordered a lot of items from you there were * bags and u brought only * bag. He argued saying no you are our regular customer you have ordered only this much . I told him to check again n he checked and called me back. He told me that they have new staff there and he forgot to pack my other items. How am I supposed to pay for the mistake of swiggys own employees? I again emailed them explaining everything. I even called the customer support but still they are saying the same thing that they won't be able to help me.