But Linda Rolph, General Secretary of the Advance Trade Union, said: “On-call contracts for customer service advisors have been a feature in Abbey and then Santander over many years. They should not be confused with zero-hours contracts... These arrangements are ideal for students and colleagues such as maternity leavers wanting to continue to use their experience but without committing to regular fixed hours. Many On Call staff in our experience take on additional hours when it is right for them.”