Flipkart — Online mobile purchase with exchange of old phone but old phone not picked

I purchased new real me phone 10 pro online through flip kart on 28 may 2023 with exchange offer of my old redmi note 5 pro the payment was made by credit card. The new phone was delivered but the old phone was not picked by the company. While order new phone the date of picking old phone was showing 12 june but on 7 june suddenly in evening 5 pm one call came to pick the old phone and told today is last day for picking, i was out of station and told him to come as per the date mentioned on flip kart application i. E on 12 june but the company cancelled to pick and on 8 june cancelled message came to pick phone. I since then 8 june, i am continuously calling and following with the flip kart but they are giving same reply again & again to sell the phone in sell back option in their application. I am telling that in sell back option only rs. 2500/- showing for my old phone instead of rs. 4150/- as was showing in exchange. They closed my complaint and now they are not replying and not giving that price as equal to when i ordered new phone with exchange value of rs. 4150/- for my old phone.