When talking about membership, we often use the phrase "was a member of" to indicate someone's affiliation with a particular group or organization. However, there are plenty of synonyms for this phrase that can help add variety and nuance to your writing. Some options include "belonged to," "joined," "enlisted in," "signed up for," "became a part of," "enrolled in," "was admitted to," "was accepted into," and "was part of." Each of these synonyms can help you convey a slightly different meaning, so choose the one that best fits the context in which you're using it.