Hello @hosuna
Thank you for your message!
For now, the job.pickups.contact.phone and the job.dropoffs.contact.phone fields are lists that only allow numerical characters using the phony 39 library following the E.164 15 recommendation. You can check here how to format phone numbers.
However, you can add the normal phone there (because it is a mandatory field for approximative addresses) and also the phone with the extension in the job.pickups.comment or job.dropoffs.comment strings as they are visible to the courier.
Don’t hesitate checking the screens of the Courier Mobile App here too.
Cheers,