The conversion is lossy since lowercase ss (e.g Gasse) is valid and common German and capitalizes to SS as well. Short of the call learning some German, there's no neatly reversing this.
For additional fun: Swiss German doesn't use ß at all, so there is no difference between "in Maßen genießen" (to enjoy in moderation) and "in Massen genießen" (to enjoy in large amounts).