For iPhone users:
If you have an iPhone, you will need to contact the company that issued your charge card. Ask them for the UID number.
For NFC-capable Android smartphones:
If you have an Android phone with NFC capabilities, you can easily find the RFID code of your charge card yourself. Here’s how:
Download the NFC Reader app from the Google Play Store.
Open the app.
Press Scan a tag.
Place the charge card at the back of your phone.
Wait for your phone to read the card.
The RFID code will be displayed under the label ID (dec).
And that's it! You now have your RFID code!