Swiggy Bundl Technologies Pvt Ltd - Charged extra so asked to cancel entire order bill has been added to my account as cancellation fee

Ordered worth ₹*** with offer applied,after placing order again added extra items through customer care worth ₹**, but I received message saying "you have pay extra ₹*** for extra added item" then immediately contacted customer care they said my mistake you received message that you have pay ₹***,then he said now you have to pay only ₹**,but delivery person demanding to ₹*** rupees,since he is demanding more money I told to cancel the order,order has been cancelled but, Swiggy has added full order value i.e ***+*** =₹*** as cancellation fee in my Swiggy account,no resolution is provided by Swiggy till now, they are just saying "feel bad that you are going through this. Trust me, this doesn't happen often. We'll do our best to ensure you only get the best experience with Swiggy going further."