price by category how to disable parent category select
i have choose a price by category
i have a parent category named "painting"
i have 3 sub category
"small" 1€ by ads
"medium" 2€ by ads
"big"3€ by ads
but when customer add an ads he can chose the category painting and post an add for 0€
i whant the customer choose only the sub category of painting
how can we do that?