Can I get in trouble for posting my prank callers number on social media?

[Jay]

Not sure if you are from the US or Australia, as you have posted from both. I'll assume the US.

The cell phone is owned by an adult, although it may be used by a minor.

There is nothing illegal about posting such a cell phone number, as you plan to. I'd caution against going too far. A simple: "I keep getting vulgar calls from xxx-xxx-xxxx. If you know who this is, please let me know" will not violation any laws.

There are existing websites devoted to this very thing. They go under names like "who called me?" and let people post information about being called from a specific phone number.

I'd think, if you have a number and a pattern of calls, the police would be able to at least speak to this person. I also wonder if you've tried calling it, perhaps from a phone with a blocked number, just to find out who answers.