Upgrade Reversal

I received a faulty device (Samsung Galaxy S6) after my online upgrade. The device was collected on 12 January, and the reversal was submitted on 20 January. The reversal should have been finalised in 24 hours, but has not!<br> I have been transferred from one department to the other, and no one seems to be able to help me. <br> How can I escalate the matter?