I want to set a serviceaccount authorizations by associating it to a clusterRole but restricted to a namespace using a rolebinding.

I declared one clusterrole and I configured a rolebinding in a namespace pointing to that clusterrole. However when I access the cluster with the serviceaccount token defined in the rolebinding I'm not restricted to the namespace.
On the other hand, when I'm accessing the cluster with a "User" certificate, this is working. I have only access to the namespace.

Kubernetes v1.13.5

The Rolebinding I defined:

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: exploitant
  namespace: myNamespace
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: view
subjects:
- kind: ServiceAccount
  name: default
  namespace: myNamespace
- apiGroup: rbac.authorization.k8s.io
  kind: User
  name: myUser

This is what I get:

kubectl auth can-i --token=XXXXXXXX get po -n myNamespace
yes

--> as expected

kubectl auth can-i --token=XXXXXXXX get po -n kube-system
yes

--> not expected !!!