It's frightening to get calls like that, especially when one is abruptly jolted out of sleep and vulnerble to to the psychological attack. I was unlucky enough to attract a couple of stalkers when I was in my early twenties. I'm not sure if getting their phone calls was harder or easier because I knew who they were. One was a co-worker who backed off when an imposing mutual acquaintance warned him it wasn't in his best interest to continue hassling me. The other was a friend's husband who had a thing for dancers. Awkward. That stalking didn't end until I moved out of town and didn't leave a forwarding address. Ran into him years later and he made a point of telling me how furious his wife was that I had "enticed" him. I suspect she knew the truth, but it was easier to blame me.
Ah, sweet days of youth.