Hi @mariol
Thank you for the question.
Due to the nature of the data, it is not possible to use WP functions to query sub field values. The problem centers around the data naming convention which requires a ‘SQL LIKE’ search on the meta_key which these functions do not allow.
The flexible content fields save their data in this format: $ParentName_$RowNumber_$ChildName
You can read up more on this here: http://www.advancedcustomfields.com/resources/querying-the-database-for-repeater-sub-field-values/
