In this workshop we will take a look at the payment service provider migration Stadtwerke Munich undertook for its mobile online payments. After setting the scene, we will follow the journey of the team responsible for the M-Login payment component, the technical integration layer between all services connected to the company-wide customer login M-Login and our payment service providers. We will highlight critical aspects of a live migration of almost half a million users, discuss options and see how the team dealt with surprises along the way in an agile manner. The workshop is intended as an interactive format presenting a series of real situations in which participants can and should weigh in with their own ideas and opinions before the actual resolution chosen by the team is presented.