To see what network(s) your container is on, assuming your container is called c1:
$ docker inspect c1 -f "{{json .NetworkSettings.Networks }}"
To disconnect your container from the first network (assuming your first network is called test-net):
$ docker network disconnect test-net c1
Then to reconnect it to another network (assuming it’s called test-net-2):
$ docker network connect test-net-2 c1
To check if two containers (or more) are on a network together:
$ docker network inspect test-net -f "{{json .Containers }}"