If the requirement is completely free, then WhatsApp Web UI automation is usually the simplest option. Most WhatsApp Business API providers (Meta, Twilio, etc.) are paid and may have messaging limits or charges.
If you have access to Integration Service, you can check whether the WhatsApp connector meets your needs:
For a free solution:
- Read numbers from Excel.
- Open WhatsApp Web using
wa.me/<number>. - Send messages using UI Automation activities.