Cpp code on Default Constructor?

Default Constructor
 
 

const double CALL_RATE = 1.0;

class Customer {
  int m_id;
  std::string m_name;
  std::string m_phone;
  double m_balance;

  public:  

  Customer(int id, std::string name, std::string phone, double balance) {
    m_id = id;
    m_name = name;
    m_phone = phone;
    m_balance = balance;
  }
  Customer(int id, std::string name, std::string phone) {
    m_id = id;
    m_name = name;
    m_phone = phone;
    m_balance = 500;
  }

   Customer() {
    m_id = 1001;
    m_name = "";
    m_phone = "";
    m_balance = 100;
  }
  void makeCall(int nmins) { m_balance -= nmins * CALL_RATE; }
  void recharge(double amount) { m_balance += amount; }
  double getBalance() { return m_balance; }
  void display() {
   //print m_id,m_name,m_phone, m_balance
  }
};
int main() {
 Customer c1(1001, "Scott", 500.0);
 c1.makeCall(10);
 c1.recharge(100);
 c1.display();

 Customer c2; 
 c2.display();
 return 0;
};