Firstcry.com — Wrong product delivered and I can't even contact customer care for a timely exchange

I have received wrong item. I have ordered small size diapers however received XL. First this is a non returnable item and now the biggest problem is not only this, I can't even contact customer care for a timely exchange of this item. Call support is not working due to covid, agreed but their chat support has never worked and still not working. When I am trying to raise the concern through app that is also a failure and I even registered a complaint once however it's still in the same condition. PS I am using latest version of app. I don't understand why the UI of this big shot app is such annoying. Now somehow I am able to raise concern since it's something I needed on urgent basis, and for this they replied to contact me within 48 hours. I don't understand how they prioritising their issues when someone need assistance as soon as for some essential item, and they are giving assurance of 48 hours. I am regular customer for first cry and regular online buyer but I have never felt this helpless with any other app and this is not happen with me first time in firscry otherwise I wouldn't be this dis-appointed.