How to add Traffic route for new services with kuma?

Hello All I´m new at Kong and Kuma. We have installed kong and kong mesh in our k8s clusters. This was already installed some months ago.
Our cluster has already deployed multiple microservices.

I´m able to see that there is a default traffic permission all to all * to *.

I would like to implement new traffic rules for the services that are already deployed in k8s. For example in namespace Foo I would like that microservices in that namespace can talk only to each other inside that namespace.

Question is…if I remove the default traffic permission , all services will unable to connect to each other I guess as a starter right?
So how can I start adding new traffic permissions for for example Service A Only can talk to Service B in Foo namespace without removing the default one ( all to all).

I mean If I create the new traffic permission for example like this:

    - match: 'service_A'
    - match: 'Service_B'

This won´t work as the “all to all” is going to have precedence right?

What is the best way to start adding traffic routes without disrupting already running microservices in the k8s cluster where kuma was already installed?

Thank you