Primary Listing Category on Results Pages

Hi guys.

On the search results pages on my site each listing has a primary listing category link underneath the business name.

https://www.travelmanagementcompanies.com/?s=&location–1=&advanced_search=yes

It seems to be defaulting to the first alphabetical category every time.

Is there any way to disable this?

Or failing that can I change it to a different category? I’ve tried doing this in the listing manager where it says ‘Make Primary’ next to each category but it makes no difference.

Thanks.