下面这个程序我做到修改就做不下去了，求高手帮帮忙啊，小弟一定感激涕零
mobilbook.txt为磁盘文件，见附件

下面是程序
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
string a[140000];
int main( )
{
    int tag=0;
menu:
    cout<<" ____________________________________  "<<endl;
    cout<<"&   欢迎使用手机号码归属地查询系统   & "<<endl;    
    cout<<"|         请选择要进行的操作         | "<<endl;
    cout<<"|                                    | "<<endl;
    cout<<"|                                    | "<<endl;
    cout<<"|                                    | "<<endl;
    cout<<"|                                    | "<<endl;
    cout<<"|                                    | "<<endl;
    cout<<"|                                    | "<<endl;
    cout<<"|      1 查询          2 添加        | "<<endl;
    cout<<"|                                    | "<<endl;
    cout<<"|      3 修改          0 退出        | "<<endl;
    cout<<"&____________________________________& "<<endl;
    int choice;
    cin>>choice;
    if (choice>3||choice<0)
    {cout<<"无此选项，请重新选择！"<<endl;
     goto menu;
    }
    
    switch (choice)
 {
    case 0:goto o;
    case 1:goto find;
    case 2:goto add;
    case 3:goto update;   
 }
find:
 {
  //查询代码
  int    i=0;
  char s[8];///="1394831";
    //将string 转换char[]     cout<<s1.c_str()char m[8];strcpy(m,s1.c_str());
  ///string   s1   =   &(s[0]);

  cout<<"请输入查询手机号码前7位"<<endl;
  cin>>s;
  string   s1   =   &(s[0]);
  ifstream infile("mobilbook.txt");
//定义输入文件流对象，以输入方式打开磁盘文件f1.dat
  if(!infile)
  { cerr<<"open error!"<<endl;
    exit(1);
  }

  while(!infile.eof())
  {
    infile>>a[i];
    if (s1==a[i].substr(0,7))
    {
      cout<<a[i]<<endl;
      tag=1;
      break;
    }
  }
  infile.close();
  if(tag==0)
  cout<<"无此号码!"<<endl;//循环执行完
    cout<<" _______________________  "<<endl;
    cout<<"|   请选择要进行的操作  | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   Y 继续查询          | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   N 返回主菜单        | "<<endl;
    cout<<"|_______________________| "<<endl;
    char ch;
    cin>>ch;
    if(ch=='Y' || ch=='y') goto find;
    else
    {    system("cls");            //清屏
        goto menu;
  }
   
     
    }

add:                                //添加
 { int    i=0;
  char s[8];            //定义一个号码段数组
  char c[50];            //归属地数组
   cout<<"请输入要添加的手机号码前7位:"<<endl;
   cin>>s;
  string   s1   =   &(s[0]);
  ifstream f1("mobilbook.txt");

  while(!f1.eof())
  {
    f1>>a[i];
    if (s1==a[i].substr(0,7))
    {
      cout<<endl<<a[i]<<endl<<" 此号码已存在，请确认输入无误"<<endl;
      goto a;
a:
    cout<<" _______________________  "<<endl;
    cout<<"|   请选择要进行的操作  | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   Y 继续添加          | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   N 返回主菜单        | "<<endl;
    cout<<"|_______________________| "<<endl;
    char cho;
    cin>>cho;
    if(cho=='Y' || cho=='y') goto add;
    else
    {    system("cls");            //清屏
        goto menu;
    }
    break;
    }
  }
      
  if(f1.eof())
    cout<<"查询完毕，数据文件中无此号码，可以继续添加"<<endl;
  f1.close();
  ofstream outfile("mobilbook.txt",ios::app);
    cout<<"请继续输入该号码的归属地(如:中国,呼和浩特):";
    cin>>c;
    cout<<endl<<endl;
    string   c1   =   &(c[0]);
    cout<<"您输入的号码及归属地为:"<<s<<","<<c<<endl;

    cout<<" _______________________  "<<endl;
    cout<<"|   请选择要进行的操作  | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   Y 确认并保存        | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   N 不保存            | "<<endl;
    cout<<"|_______________________| "<<endl;
    char ch;
    cin>>ch;
    if(ch=='Y' || ch=='y') goto y;
    else goto menu;
y:
    outfile<<"\n"<<s<<","<<c;
    cout<<"存储成功!"<<endl;
  goto a;
 }

update:                            //修改代码
{  int    i=0;
  char s[8];            //定义一个号码段数组
 cout<<"请输入要修改的手机号码前7位:"<<endl;
   cin>>s;
  string   s1   =   &(s[0]);
  ifstream f1("mobilbook.txt");

    while(!f1.eof())
  {
    f1>>a[i];
    if (s1==a[i].substr(0,7))
    {
        //cout<<"您要修改的电话号码及归属地为: "<<a[i]<<endl;
      tag=1;
        

      break;
      if(tag==0)
    cout<<"无此号码!"<<endl;
    cout<<" _______________________  "<<endl;
    cout<<"|   请选择要进行的操作  | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   Y 继续              | "<<endl;
    cout<<"|                       | "<<endl;
    cout<<"|   N 返回主菜单        | "<<endl;
    cout<<"|_______________________| "<<endl;
    char ch;
    cin>>ch;
    if(ch=='Y' || ch=='y') goto update;
    else
    {    system("cls");            //清屏
        goto menu;
    }
    }
    
  }
  
  
 goto menu;
}
o:
cout<<"\n\n\t欢迎再次使用手机号码归属地查询系统\n\n";
return 0;
}