lol just checked the trade in my S9+

estimated trade in value RM0 rofl

It is not for any phone. There is a list of devices that are acceptable for trade in when you apply for it.

If the device is too old, it won't be listed. The trade in process is:

1. Enter Zip Code
2. Select device type
3. Select manufacturer
4. Choose your device model from a list available
5. Enter the IMEI

The good thing is the list is quite extensive, just not so extensive that you can trade in any old device you have lying around.