IMEI checker returning false even with compatible device.

user_jhieyu, hello there and thanks for reaching out. I completely understand your concern. Especially when aiming for that amazing perk! I'd like to get to know more about your device. I understand that these devices can be the same but it's all about the inside of the device and it's compatability. I'd like to take a deeper dive into this with you. To move forward with your concern, please send us a direct message with your full name and complete service address. From there I can authenticate your account and assist you further.  

To send a direct message, please click on the chat icon in the top-right corner of the screen, and select "Xfinity Support" to initiate a live chat. 
Click "Sign In" if necessary
Click the "direct messaging" icon
Click the "New message" (pencil and paper) icon
Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list which appears. The "Xfinity Support" graphic replaces the "To:" line
Type your message in the text area near the bottom of the window
Press Enter to send it.