RFID tags

Hiiii every one please i need a help
i'm using RFID sensor to read 4 tags , and after read and print the tag number it must print that name of this tag .

now what happened with me the sensor read the tag is number, and print it,but just one time he print the tag is name the only at the first time when i run the code .

so pleas i need a help how can the sensor read the tag is number then the name of this tag

#include <SoftwareSerial.h>
SoftwareSerial RFID(2, 3);
String tag[] ={"25653484848574968675753563","25653484848575250685549573","25653484849526669575166673","25653484849526554554852553"};
String pos[]={"25 path A","11 path B","87 path C","08 path D"};
String T = "";
String x="";
int data=0;
void setup()
{ 
  RFID.begin(9600); 
    Serial.begin(9600);
}
void loop()
{
 
  if (RFID.available()>0)
  {
   delay(100);
   for ( int z=0 ; z<14 ; z++)
    {
      data=RFID.read();
      Serial.print(data);
      T=T+data;
      
    }
     Serial.println(" ");       
  delay(1000);  
    RFID.flush();
  }
    for ( int i=0 ; i<4 ; i++)
    { 
      if(T==tag[i])
    {
      x= pos[i];
      Serial.println(x);
    }
   
    }
}

The String T start as "" then you concatenate 14 characters with it. Where in the code to do set it back to "" before reading the next tag ?

By the way, do the number of characters in the tag array match the number of characters that you are reading from the tag ?