Check your phone. I have a friend who's number is all that shows up whenever he calls or texts even though his name is listed in my phone book. His is the only contact that this happens to. iPhone 6 here also.
I had a similar issue with my android.
It happened to be that I saved that 1 contact onto the simm, and the others were all saved on the device.
I don't know if that helps with an Iphone (I sure hope it does)..