Ive tested this in the API explorer as well as with the following command line invocation:

curl -X GET --header "Content-Type: application/json" --header "Accept: application/json" https://agv.nationbuilder.com/api/v1/sites/agv/pages/events/\?id\=...\&access_token=...

Both produce contact phone numbers with the first number missing

e.g. 0411222333 is given as 411222333

Viewing the event via http://victoria.greens.org.au/ocean_grove_doorknock_and_snack 

we see that the correct, full phone number is displayed.

Can you please fix this?