Faithful in My Fashion

Faithful in My Fashion is a 1946 film. Jeff Tom Drake arrives home to New York City after being away in the Navy for several years. Unaware that his fiance, Jean Donna Reed, is now dating a man Warner Anderson at the department store where she works, Jeff assumes she is still intends to marry him. In order to save Jeff from heartache, several employees at Jeans store set up a ruse to keep Jeff unaware of Jeans new man until he is deployed again. Jean cooperates with the ruse, but it isnt long before secrets get revealed.

Source: Wikipedia