Почему нету вывода с функции Users.ShowList()? [закрыт]

#include <iostream>
#include <string>
using namespace std;
struct Abonent {
string Name;
string Number;
Abonent* next;
Abonent(string _Name, string _Number) {
    Name = _Name;
    Number = _Number;
    next = nullptr;
}
Abonent() {
    next = nullptr;
}
};
struct List {
    Abonent* head;
    List() {
    head = nullptr;
    }
    void Add(Abonent* newAbonent) {
    if (head == nullptr) {
        head == newAbonent;
    }
    else {
        Abonent* current = head;
        while (current->next != nullptr) {
        current = current->next;
        }
        current->next = newAbonent;
    }
    }
    void ShowList()
    {
    if (head != nullptr) {
        Abonent* current = head;
        while (current->next != nullptr)
        {
        cout << "Name: " << current->Name << endl;
        cout << "Number: " << current->Number << endl;
        current = current->next;
        }
    }
    }
}; 

int main() {
Abonent user1;
user1.Name = "Yana";
user1.Number = "380921091";
struct Abonent *Yana; 
Yana = &user1;
Abonent user2;
user2.Name = "Vitalya";
user2.Number = "3800989381";
struct Abonent *Vitalya; 
Vitalya = &user2;
Abonent user3;
user3.Name = "Kolya";
user3.Number = "380992034";
struct Abonent *Kolya; 
Kolya = &user3;
Abonent user4;
user4.Name = "Anton";
user4.Number = "380992034";
struct Abonent *Anton; 
Anton = &user4;
List Users;
Users.Add(Yana);
Users.Add(Kolya);
Users.Add(Vitalya);
Users.Add(Anton);
Users.ShowList();
cin.get();
return 0;
}