Unfortunately, Minecraft themselves don't allow private messaging on official Minecraft server partners "to allow more thorough moderation across all parts of the server", and due to privacy and security reasons.
I believe that the fact that it's still in the /f help command list is either something they might have forgotten to remove, or confused with Minecraft Java Edition. I do believe this is confusing and should be removed from /f help on Bedrock Edition.
You can find all (truly) available commands on the
Bedrock Command List.
Read the communication by Minecraft themselves about this topic
here.