Unknown error occured (-1) when trying to restore iphone 7

My error message was (-1). I tried 1,2,3,and 4. I also contacted apple support and was on the phone with them twice for over an hour each time, with each representative asking me to do the same steps over and over again. I even tried to restore the iphone on a different computer with the same results. I was told by the apple store that the no service issue was a known defect on the iphone 7 and it would be under warranty but I had to send it in first. The first time I sent it in they sent it back saying that they could not duplicate the problem, probably because as of now the phone is frozen, so of course they can't see the "no service" issue I had with it.

Yes, I did send the phone in for the second time but I haven't heard anything yet from them. I'm afraid i will be out the almost $300 I paid for it (it was pre-owned) cause I didn't buy the insurance. I will update when I find out their answer.