Adidas — Refund and Return

I have ordered Tank Top from Adidas official website on 29th july 2022. I have received the said order just after 2days.
Because of the size was too big for me i wanted to return the product. At the time of Product delivery i have paid them via COD.
Yesterday i have received a message that my order has recieved back to Adidas warehouse.
But i have not got my return, neither they asked for bank details because my order was COD.
I have tried them call 100 of times but the number provided on their website is useless, it's systems generated call and it gets cut automatically within 10sec.
I have aslo tried to mail them but this is also system generated mail and there they provide me a reference number and they say we will get back to you in 2-4 business days but it never happens.

Help