There is a special procedure to activate the 4G LTE service on your RFinder with AT&T Wireless:
Send an e-mail to firstname.lastname@example.org with W2CYK@rfinder.net in CC.
SUBJECT: M1 CONVERT TO LTE
«JOSH, PLEASE CONVERT MY M1 TO LTE.
MY IMEI IS: <PUT YOUR IMEI HERE>
MY PHONE NUMBER IS: <PUT THE PHONE NUMBER OF OF YOUR M1 HERE>
MY AT&T PIN IS: <YOUR AT&T 4 DIGIT PIN>
THANKS FOR YOUR SUPPORT!
YOUR NAME AND YOUR CONTACT NUMBER»
Then, you just need to wait up to few days until the activation is in place. Enjoy your RFinder LTE capabilities.
Such procedure is not necessary in other countries.