Wow....you message is depressing and is further evidence that we've been duped- just as other have suggested. TO me, this is worse than a nursery mislabeling a tree- though that is careless and a bad thing- I'd like to think its usually an honest accident or a lazy employee who does it. What is happening with these mulberries seems a bit ore sinister to me. I've seen people say they have called and questioned Willis, only to be told "oh no, its what you ordered". After all this time, and probably even more calls, they must realize what they are doing. The fact that yours was a Persian and mine a black beauty makes it look even worse for them. It seems like they are just growing a bunch of native persimmons and sticking whatever order they have on them. I have no proof of this....just basing it on observations and comments from you, myself, and others here.
TO answer your question, I still have no idea what mine is, but its 3 years old, over 10 foot tall, extremely bushy/vigorous, and it has mostly leafed out already this year with no signs whatsoever of flowing/fruiting. Like you, I'm extremely disappointed and frustrated. I don't know how hard mulberries are to graft, but I will likely top work mine next year if I can find some kind soul to help with some scion wood.
Good luck with yours. If you contact Willis I'd sure like to hear what they tell you!