Bagaimana cara mencari kontak dalam buku telfon berdasarkan nomor telfon

// Phonebook project
//===============================

#include <iostream>
#include <conio.h>
#include <string>
using namespace std;

//prototypes
void printline(char, int);
bool name_valid(string);
bool mob_valid(string);

class contact
{
    string name;
    string mob;
    public:
    	//Initialize the contact by a default value
        contact(): name(""), mob("")
        {}

        // Shows all contacts
        bool show()
        {
            if(name != "")
            {
                cout << name << "\t" << mob << endl;
                return 1; //Indicates success
            }
            else
                return 0; //Indicates failure
        }

        //Search
        bool show(string search_term)
        {
            if(search_term == name)
            {
                cout << name << "\t" << mob << endl;
                return 1;
            }
            else
                return 0;
        }

        //Checks whether the name exists or not
        bool name_exists(string tname)
        {
            if(tname == name)
                return 1;
            else
                return 0;
        }

        //The contact object is initialized by valid values
        bool add(string new_name, string new_mob)
        {
            if(name=="")
            {
                name = new_name;
                mob = new_mob;
                return 1; // Success
            }
            else
                return 0; // Failure

        }

};

int main()
{
	contact person[100];

	string temp_name, temp_mob;
	int choice, i, counter;
	bool flag;
	bool cancel_flag;

	cout << "**** PHONEBOOK ******" << endl;

	do
	{
		cout << "\n\n\n";
		printline('-', 20);
		cout << "1. Memasukkan Data" << endl
			<< "2. Menampilkan Data" << endl
			<< "3. Mencari Data Berdasar Nama" << endl
			<< "4. Mencari Data Berdasar No. Telfon" << endl
			<< "5. Keluar" << endl
			<< "Masukkan Pilihan Anda : ";
		cin >> choice;

		system("cls");
		printline('-', 20);
		cancel_flag = 0;
		flag = 0;
		counter = 0;

		switch (choice)
		{
		case 1:
			cout << "Add New Contact\t\t\t\tpress $ to cancel" << endl;
			printline('-', 20);
			counter = 0;

			//Berulang hingga nama dan no benar
			do
			{
				flag = 0;
				if (counter)
					cout << "Try again\t\t\t\tpress $ to cancel"
					<< endl;

				//counts how many times the do-while loop executes
				counter++;

				cout << "Name: "; cin >> temp_name;

				//Cancel operation
				if (temp_name == "$")
				{
					cancel_flag = 1;
					break;
				}
				cout << "Mobile No.: "; cin >> temp_mob;

				//Cancel operation
				if (temp_mob == "$")
				{
					cancel_flag = 1;
					break;
				}

				//Check whether name exists
				for (i = 0; i<100; i++)
					if (person[i].name_exists(temp_name))
					{
						cout << "Kontak sudah ada!"
							"Masukkan nama lain."
							<< endl;
						flag = 1;
						break;
					}

			} while (!name_valid(temp_name) ||
				flag ||
				!mob_valid(temp_mob));

			if (cancel_flag)
			{
				system("cls");
				break;
			}

			//Memasukkan kontak ke buku telfon
			for (i = 0; i<100; i++)
				if (person[i].add(temp_name, temp_mob))
				{
					cout << "Berhasil Menambah Kontak" << endl;
					flag = 1;
					break;
				}

			if (!flag)
				cout << "Memory Kontak Penuh! Hapus Beberapa Kontak."
				<< endl;
			break;

		case 2:
			cout << "Menampilkan Kontak" << endl;
			printline('-', 20);

			for (i = 0; i<100; i++)
				if (person[i].show())
					flag = 1;

			if (!flag)
				cout << "Tidak ada kontak yang ditemukan!" << endl;
			break;

		case 3: //search contact by name
			do
			{
				if (counter)
					cout << "Coba lagi" << endl;
				counter++;
				cout << "Cari Nama : \t\t\t\tpress $ to cancel\n";
				cin >> temp_name;

				//Cancel Operation
				if (temp_name == "$")
				{
					system("cls");
					break;
				}

				for (i = 0; i<100; i++)
					if (person[i].show(temp_name))
					{
						flag = 1;
						break;
					}

				if (!flag)
					cout << "Kontak tidak ditemukan" << endl;
			} while (!flag);

			break;

		case 4: //search contact by number
			do
			{
				if (counter)
					cout << "Coba lagi" << endl;
				counter++;
				cout << "Cari Nomor : \t\t\t\tpress $ to cancel\n";
				cin >> temp_mob;

				//Cancel Operation
				if (temp_mob == "$")
				{
					system("cls");
					break;
				}

				for (i = 0; i<100; i++)
					if (person[i].show(temp_name))
					{
						flag = 1;
						break;
					}

				if (!flag)
					cout << "Kontak tidak ditemukan" << endl;
			} while (!flag);

			break;

		case 5:
			return 0;
			break;

		}
	} while (1);

	_getch();
	return 0;
}
//prints a line
void printline(char ch, int size)
{
	for (int i = 0; i<size; i++)
		cout << ch;
	cout << "\n";
}

//Contact name validation
bool name_valid(string tname)
{

	if (tname.size()>20)
	{
		cout << "Nama Salah!\nMasukkan Maks 20 Karakter dan Tanpa Spasi!"
			<< endl;
		return 0;
	}
	else if (tname == "")
	{
		cout << "Nama Salah!\nNama tidak boleh kosong!" << endl;
		return 0;
	}
	else
		return 1;
}

//mobile number validation
bool mob_valid(string tmob)
{
	if (tmob.size()>13 || tmob.size()<10)
	{
		cout << "Nomor salah\n"
			"Masukkan Nomor Antara 10 - 13 digit" << endl;
		return 0;
	}
	else if (tmob == "")
	{
		cout << "No salah\n"
			"Nomor tidak boleh kosong" << endl;
		return 0;
	}
	else
		return 1;
}

Case nomor 3 adalah untuk mencari kontak berdasarkan Nama, berjalan baik, tapi untuk Case nomor 4 yang merupakan program untuk mencari kontak berdasarkan Nomor Telfon tidak bisa, ada yang bisa bantu? Tolong berikan contoh program untuk Case 4 yang bisa, terimakasih