According to Fox News:
“He reached several White House operators before being told the president would call him back. According to the comedian, senior White House adviser Jared Kushner returned the call, connecting him to Trump.”
The call should not have been returned until verified. It reveals very lax security by some staff members to say the least. It won’t happen again.
However, even if the call had not been returned - the ‘comedian’ initiated the call while impersonating a US senator - for the purpose of gaining access to the president and talking policy.
I’m not an attorney, but the man could possibly be charged with a felony and face prison time and/or fined.