WhatsApp will it message my contacts How does pairing work

No. Default WhatsApp DM policy is pairing. Unknown senders only get a pairing code and their message is not processed. OpenClaw only replies to chats it receives or to explicit sends you trigger.
Approve pairing with:
openclaw pairing approve whatsapp <code>
List pending requests:
openclaw pairing list whatsapp
Wizard phone number prompt: it’s used to set your allowlist/owner so your own DMs are permitted. It’s not used for auto-sending. If you run on your personal WhatsApp number, use that number and enable channels.whatsapp.selfChatMode.