For pre-filling the phone number field via URL parameters, the Field code can be found under the Advanced properties.
The phone number field has 2 supported attributes. Country and number
To pre-fill these attributes, you can use the field code along with the attribute.
phone.country (It supports only iso2 country codes.)
phone.number
Using the above, we can append the URL parameters to the form's URL:
https://example.neetoform.com/8abc2aa31ef7d12f288e?phone.country=IN&phone.number=7645234569