萌新求助

我运行下面的之后可以创建一个txt文件并写入东西，但读取的时候就是读取不到，求大佬帮忙解决。谢谢!
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main()
{
char op;
char filename[100];
char telnum[100];
char street[100];
char city[100];
FILE *fp;
printf("CUSTOMER BILLING SYSTEM:\n\n=================================\n\n1: to add account on list\n2: to search customer account\n3: exit\n\n=================================\n\nselect what do you want to do?:");
scanf("%s",&op); switch(op)
{
FILE *fp;
case '1':
printf("Input name:");
scanf("%s",filename);
strcat(filename, ".txt");
if((fp=fopen(filename,"w+"))==NULL)
{
printf("error\n");
exit(0);
}
printf("Input mobile no:");
scanf("%s",telnum);
fputs(telnum,fp);
fputc('\n',fp);
printf("Input street:");
scanf("%s",street);
fputs(street,fp);
fputc('\n',fp);
printf("Input city:");
scanf("%s",city);
fputs(city,fp);
fputc('\n',fp);
fclose(fp);
return 0; int telnum,street,city;
int i; case '2':
printf("Enter account name:");
scanf("%d",filename);
if((fp=fopen(filename,"r"))==NULL)
{
printf("error\n");
exit(0);
}
fscanf(fp,"%d",&telnum);
for (i=0;i<1;i++)fscanf(fp,"%*[^\n]%*c");
fscanf(fp,"%d",&street);
for (i=0;i<2;i++)fscanf(fp,"%*[^\n]%*c");
fscanf(fp,"%d",&city);
printf("telnum:");
printf("%d\n",telnum);
printf("street:");
printf("%d\n",street);
printf("city:");
printf("%d\n",city);
fclose(fp);
}
return 0;
}