Fetch json array in PostgreSQL procedure - json

Question

I'm using PgSQL9.6.
I have procedure named as createBooking in PgSQL. It receive few parameters and one of them is additional type text.
Request is
{
"email": "user2#name.com",
"start_date": "2016-10-21 11:00:00+00",
"end_date": "2016-10-21 15:00:00+00",
"guests": 50,
"firstname": "User",
"lastname": "Name",
"payment_type": "Method 1",
"phone": "[phone]",
"user_id": 22,
"y_id": 3,
"additionals": [
{
"extrasId": 6,
"money": 19750,
"packageId": null,
"amount": 3
},
{
"extrasId": 11,
"money": 64380,
"packageId": null,
"amount": 5
},
{
"extrasId": null,
"money": null,
"packageId": 3,
"amount": 1
}
]
}
I'm trying fetch 'additioanl'.
FOR i IN SELECT json_array_elements(createBooking.additional)
LOOP
sum := sum + i->>'money';
END LOOP;
It does not mater what is in body of loop.
When I calling this function via PostMan it is sending me response with error.
{
"hint": "No function matches the given name and argument types. You might need to add explicit type casts.",
"details": null,
"code": "42883",
"message": "function json_array_elements(text) does not exist"
}
Can some body explain me how should I fetch it?
Thank you.