Hey Benson, you can assign the caller ID to your destination when you define your transfer call function.
curl -X POST
\\
-H "Authorization: Bearer " \\
-H "Content-Type: application/json" \\
-d '{
"type": "transferCall",
"destinations": \[
{
"type": "number",
"number": "insert-phone-number-id-here",
"callerId": "{{customer.number}}",
"numberE164CheckEnabled": false
}
\]
}'