Heat oil in a big stock pot or pan and fry the onions and garlic till the onions turn translucent.
Add the carrots and celery and fry till fragrant.
Add the crushed tomatoes and beans, season with salt, pepper and oregano.
Lastly add the pasta and the green beans and pour in the chicken stock. Check for seasoning. Cook for about 5 to 10 minutes, till the pasta softens.