Have you tried setting POSTGRES_DB variable in your docker-compose.yml environment ?

 image: postgres
    environment:
      POSTGRES_USER: ${POSTGRES_USER:-postgres}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-changeme}
      POSTGRES_DB: premiership
      PGDATA: /data/postgres
    volumes:

see https://hub.docker.com/_/postgres :

POSTGRES_DB

This optional environment variable can be used to define a different name for the default database that is created when the image is first started. If it is not specified, then the value of POSTGRES_USER will be used.

The Postgres environment variables and initialization scripts are only used if Postgres doesn't find an existing database on startup.

Delete your existing database by deleting the postgres_data volume and then start the Postgres container. Then it'll see an empty volume and will create a database for you using your variables and your scripts.

Have you considered using the POSTGRES_DB environment variable ?

services:
  db:
    container_name: postgres
    image: postgres
    environment:
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
      PGDATA: /data/postgres
      POSTGRES_DB: bank
    volumes:
      - db:/data/postgres
    ports:
      - "5332:5432"
    networks:
      - db
    restart: unless-stopped
    healthcheck:
      test: [ "CMD-SHELL", "pg_isready -d postgres" ]
      interval: 30s
      timeout: 10s
      retries: 5
networks:
  db:
    driver: bridge

volumes:
  db:

If, when you start your Docker Compose, you're getting:

PostgreSQL Database directory appears to contain a database; Skipping initialization

you need to proactively remove the volumes which were set up to store the database.

The command docker-compose down doesn't do this automatically.

You can request removal of volumes like this:

docker-compose down --volumes

Be warned that this will delete any data you had in any database before. You can't get this data back if you remove the volume which contained it!