Showing "Return Completed" as status but didn't receive refund yet I have ordered an IPhone and the phone was not delivered(not sure about the reason) and was returned back to apple warehouse. The status in the order page shows as "Return Completed" on 22nd of December 2018. I didn't receive the refund yet. How much longer it might take for the refund to be completed.
It can take 5-7 days once the goods arrive back at the warehouse.

From the refund page:


  Once your goods are back at Apple’s warehouse, your refund will be processed. Please allow 5-7 days for the refund to reach your account. For cash payments such as cheque and wire transfer, we will require your bank details, including IBAN/SWIFT, to proceed with the refund to your account.


If you haven't received your refund contact Apple Support. I would give it  a bit of time since it is holiday time.