Xiaomi India — Exchange of Old phone Rejected without any reason

My name is Sohail. I am a regular customer of Xiaomi from the past 5 years. I am a Diamond class user with 2833 Mi VIP Points.
I have never had this horrible experience with Xiaomi earlier. As there was some technical error while ordering from my Mi Id I ordered the phone from my brothers Mi Id.
I ordered Redmi K50i 5g Mobile, (8+256) Stealth black color with an exchange of my Redmi K20 Pro (6+128) (which was also earlier brought from Mi Store). Before ordering online i visited the local offline Mi store and asked the exchange price. The salesman downloaded cashify app enetered all the details checked my phone physically and told me the value would be 9500 Rs. But as there was no additional discount offer on the local offline store i decided to order online.
As there was no exchange available on my current address i sent the mobile to Aurangabad near my brother where the exchange was available.
But at the time of delivery the delivery guy rejected my old phone and the reason he gave was, the phone has scratches on the side frame. I told him that it was obvious that the phone would have scratches on the side frame cz its a old phone and its used. But there is no scratch on the screen. The screen is new in condition. The phone is in working condition as that was the only thing mentioned while ordering. Obviously there would be minor signs of wear and tear due to the use of the phone. But the delivery guy was not ready to accept it. I told him this is not done. I have already seen the exchange of Amazon.in & Flipkart.in and they just reduce the amount as per the phone's condition. And i am ready to pay the difference amount of 500 Rs. How do you expect the phone to be without a single scratch. But he said we only accept phones which are 3-4 months used.
I then contacted the Mi Helpline no. twice and they made my experience more horrible by just asking me the details as my name, my registered mobile no., My email id, my address, each and every time i call and they started annoying me with all the formal talks but were not ready to notice the real problem. During the first call the lady on the phone told that she sent a text message and i should upload my phone's photo's on that, i repeatedly asked her to spell out the link as i did not received the message but she never bothered. I never got the message neither she spelled the link.
Then i raised a request from My Mi Store App. In Accounts Section through Contact us option. There i was not allowed to add a message of more than 200 characters. I wrote as short as possible entered the details. Uploaded the photos. And sent it.
Then next day i received the mail and it said dont reply. In that mail they accepted that my phone is in working condition. But now what should i do? How should i exchange the phone?
And i am again mentioning that the phone is in working condition. It turns on. Its touchpad is working. It calls and does all ths functions. There is no cracked screen or physical damage. There are only some minor scratches on the body. How can u reject a phone on the basis of scratch.
I[censored] never intend to exchange the phone why just advertise all this. And its terrible that no one cares. I got a call from xiaomi for the order confirmation. Then i requested them to send me a mail about the reason of cancellation so i can take some action as i paid the amount and still they aren't delivering. But they refused bluntly that we cant send a mail. And said thank u for ur time. I request you to kindly take a look into the matter and please help me as soon as possible. This is ths first time i am so disappointed with the service of Xiaomi.