This feature is available in newer versions and is still under experimental stage.
Resizing an in-use PersistentVolumeClaim:
feature state: Kubernetes v1.15 (beta)
In this case, you don’t need to delete and recreate a Pod or deployment that is using an existing PVC. Any in-use PVC automatically becomes available to its Pod as soon as its file system has been expanded. This feature has no effect on PVCs that are not in use by a Pod or deployment. You must create a Pod which uses the PVC before the expansion can complete.
Similar to other volume types - FlexVolume volumes can also be expanded when in-use by a pod.
For more info refer to: https://kubernetes.io/docs/concepts/storage/persistent-volumes/