My messages aren't saying delivered but they've sent?

My messages aren't saying delivered after I've sent them, but they've gone through and then re-send through SMS, this only happens with one of my contacts and it's been happening with only his contact. I'll send a couple messages and he'll receive them and reply, but they never say delivered and then they do, or they never say delivered and they've already been sent through of have turned into SMS and sent again only to be sent to him a second time, I have an iPhone 5s with iOS 9.0.2 16gb.

I have tried resetting my phone, turning Messages off, deleting all of my messages. None of which fixed it, nor were temporary. What should I do?