The 15-digit IMEI (Handset ID) number that you provided is not associated with a phone or device that has a rebate card on your date of purchase. It may also not be a valid IMEI (Handset ID) number.
Actions to take:
Double check your IMEI (Handset ID) number: To find your T-Mobile phone 15 digit IMEI (Handset ID) number press *#06# on your phone and hit send. The IMEI (Handset ID) number is also found on the white sticker label required for submission (if you have a photocopy of your submission materials).
Contact T-Mobile Rebate Card Customer Care > to verify the correct IMEI (Handset ID) number was submitted (numbers were not accidentally switched or skipped).