How to update the json data stored in a text field in PostgreSQL?

I have a table services that has a column called properties whose type is text.

There is json data stored in properties column.

I can check json data with psql I like this:

SELECT * FROM services WHERE properties :: json - >> & # 39; url & # 39; = & # 39; www.example.com & # 39 ;;

But I can not update the json data with the following query:

UPDATE services SET properties :: json - >> & # 39; url & # 39; = & # 39; www.mydomain.com & # 39; WHERE properties :: json - >> & # 39; url & # 39; = & # 39; www.example.com & # 39 ;;

How can I update the url field within properties column?

What's happening with me TO UPDATE I send?