acessing docker container ip with its name in nginx - docker

Question

I'm running one container nginx_cont for frontend and one container web_cont for backend.
I would like my nginx in my frontend container to reach my backend container by its name with
proxy_pass http://web_cont:8000;
I've tried with the container ip and it is working. I 've tried with the name web_cont_1 as my docker-compose is adding number. And i've tried with web_cont_1.spa_network as I have specified networks: spa_network: in my docker-compose.yml.
I get the error :
nginx_cont_1 | 2022/06/01 12:00:23 [emerg] 1#1: host not found in upstream "web_cont_1" in /etc/nginx/conf.d/nginx.conf:12
Note that when i do docker-compose run containername commande, i get the error
ERROR: No such service: containername
containername is the name i get when i run docker-compose ps
Any hints?
this is my docker-compose.yml
version: '3.7'
services:
nginx_cont:
build:
context: .
dockerfile: ./compose/production/nginx/Dockerfile
restart: always
volumes:
- staticfiles:/app/static
- mediafiles:/app/media
ports:
- 80:80
- 3000:3000
- 6006:6006
depends_on:
- web_cont
networks:
spa_network:
web_cont:
build:
context: .
dockerfile: ./compose/production/django/Dockerfile
restart: always
command: /start
volumes:
- staticfiles:/app/static
- mediafiles:/app/media
- sqlite_db:/app/db
ports:
- 8000:8000
env_file:
- ./env/prod-sample
networks:
spa_network:
ipv4_address: 172.20.128.2
networks:
spa_network:
ipam:
config:
- subnet: 172.20.0.0/16
volumes:
sqlite_db:
staticfiles:
mediafiles:
Thank you