Rustic Chickpea soup

Name: Rustic Chickpea soup
Ingredients: 1 tablespoon olive oil; 1 sweet potato chopped into bite sized pieces; 2 celery sticks chopped; 1 onion finely chopped; 2 cloves garlic minced; 14 ounces tin chickpeas (garbanzo beans) rinsed and drained; 14 ounces chopped tomatoes; 4 cups vegetable stock; 2 tablespoons freshly chopped herbs; Salt to taste; 1/4 teaspoon chilli flakes; 1/2 cup mini pasta shells