Delhivery — My package isnt returned and its been more than a week

I had purchased a shoes from Zara and I chose to return the product on 28th November. Even after selecting return option, their delivery boy didn’t pick up the product for 3 days and after calling their executive the product was picked. Now it’s more than a week and the product haven’t reached the retailer. I bought the shoes on 16th and Zara has a 1 month return policy. If the product didn’t reach the seller before 16th I won’t get any refund. What kind of parcel service are you providing. It’s the worst one I’ve even come across. I would really appreciate if you do what’s necessary.