Apple - Iphone 11 pro max replacement

I used IPhone ** Pro max *** GB, unfortunately the phone frequently restarted with apple logo. I gave it Chennai RC centre and inturn they moved to Bangalore RC, Finally they concluded that the phone is tampered. I requested for repair or replace but they denied and suggested to go far trade In. I trade for Iphone ** mini and total cost is ***** INR and Iphone pro ** max is diagnosed and fixed the resale option for the INR ***** and they asked me to made the additional payment of ***** and I did it. During the time of delivery, one more diaganosis is done and they asked me to made additional payment of ***** to courier guy. I cancelled the order and asked to return the amount of ***** INR. The executive told me to wait for ** working days where as phone has to return to their place, from their they starts the refund.