[{"phone":"phone1","groups":[{name:"A",subscribed:false},{name:"B",subscribed:false},{name:"C",subscribed:true}]}]

db.collection.update({"phone":"phone1"},{"$set":{"groups.$[elem].subscribed":true}},{"arrayFilters":[{"elem.name":{"$in":["A"]}}],"multi":false,"upsert":false})