Final answer:
Margot is appointed as the Superintendent of five canteens at Woolwich without pay, a position given to her by Lady Londonderry.
Step-by-step explanation:
The call up that Margot receives is her appointment as Superintendent of five canteens for munitions workers at Woolwich. These canteens are managed by the 'Ladies' Legion', headed by Lady Londonderry who personally asked Margot to take on this role.
Despite the responsibility and contribution to the war effort, Margot's work as Superintendent is voluntary, and unlike her previous job at the War Office, she does not receive pay for this position. She spends five days a week at Woolwich and enjoys shorter working hours compared to her time at the hospital, along with the benefit of being outdoors which is better for her health.