Phone in for repairs for more then 3 months

I took my phone in for repairs on the 10th of July,They said it should be back by the 22nd of the same month.I have been following up on the progress of the phone but all they do is to tell me that there is no feed back and there is nothing they can do since the courier company delivered it at the wrong address.I will be taking further steps on the issue as i have been paying for almost 3 months for the service i do not have.I am a very unhappy client as they only follow up or escalate the matter when they see me.