I do not know how to “judge” this event from my childhood. I need some external feedback because I can’t judge it from an adult perspective. I’ve remembered and forgotten it throughout my life at various times, but it came up recently and I’m overwhelmed.
My therapist has not been very helpful. She switched from it being not a big deal to thinking it was "traumatic" and "sick."

When I was about 9 years old, I received an anonymous phone call. My dad answered the phone and said “it’s for you.” They knew my name. I don’t know why my dad handed the phone to me because it was a man’s voice, or at least a deep voice.
He said he had made a bet that I would come and see him naked. I was so shocked and uncomfortable. He kept trying to convince me. I kept saying “I don’t know.” I took it seriously and wanted to oblige him. There was a lot of silence and breathing which makes me think now something else was going on, but it makes me feel sick to think about it.
I don’t know how long the phone call lasted but I couldn’t say much and finally he hung up. I felt so ashamed I never told anyone. I felt guilty that I never helped the guy with his bet but also ashamed that he “chose” me, that I must have done something to cause it. I have a feeling I got more than one call but it is too foggy to remember. I also remember having a recurring dream of being kidnapped by a man. I basically pushed it out of my mind and haven’t worried about it, just labelled it as “that weird thing that happened to me.” Coming up again, it’s wrapped up in shame and fear.
Is this just a prank I should forget about it? Do you think it would be traumatic for a child? I just don’t know how to judge it from an adult perspective. Since it has come up again I’ve found it’s an actual thing, called an “obscene phone call.” I always thought it was just me. There is only limited information on obscene phone calls and children but I haven’t been able to read it yet. I start feeling quite sick and dizzy.

Thanks to all for helping me see this clearer.