Hi, I would be happy to help you with WhatsApp API approval for your own number.
Approval Time would be less than 5 days, but you need to have Facebook Business Verified (I can help you get that)
Monthly Cost would be USD 49
Session Message cost will be USD 0.001 per message
Incoming Session Messages is always free.
Let me know if you want to know more about this.
I can help you with end to end approval.
Thank you.