Get on the phone, ask for a supervisor, point out the cr*p you have already been through due to faulty equipment being sent out. Point out that you are extremely unhappy with what has happened and make sure they are aware of how close you are to moving to a new provider. Drop the word incentive into the chat a couple of times and see if they take the bait
It sounds as though someone sent a returned phone out which would point to human error/ bad training/ audit failure etc, if you decided to try one more time with them make sure they know it's their final chance. You never know what they will offer to keep a customer