Faulty phones and terrible service

A phone was sent to in November 2019, went to a Samsung store to find out why the phone memory was full and thats when I discovered the phone was an OBF (out of box failure) Samsung A7 only comes in 128GB, the one I got was 16GB, sent the phone back on Monday 25th November as I received it Thurs 21 November, money was deducted on 28 December 2019 and i still have no phone after calling most of December and having the phone hung up on me. The service is extremely appalling, I need someone help on how to sort this out.