I'm trying to migrate our WhatsApp number from a different platform to Zendesk. Is this possible?
If you own the WhatsApp business account, you can remove it from the old provider and use the self-service flow to set it up with Zendesk. Otherwise, Zendesk does not support phone number migration. You can select a new number to integrate with Zendesk.
Although, you can show your interest in Whatsapp number migration in this form: Requests for WhatsApp Number Migration.
For more information, see this article: Adding a WhatsApp channel (self-service).