Then I'm guessing it falls under one of these on that site I linked:
If your device is locked to the CDMAS network but uses GSM technology
This means your device is compatible with any network, however the device is currently locked to the CDMAS network, thereby preventing you from receiving a signal when using any other network SIM card.
Please contact the retailer where you purchased your device to see if this applies to you, and to have the device unlocked. Once your device is unlocked, it can work with any one of our remaining networks, including the comparable GSMT network.
Click here to learn more about our wireless networks.
Once your device is unlocked, visit
redpocket.com/plans to purchase a SIM card on one of our other wireless networks (like the GSMT, GSMA, or CDMA-V network). Once you've received your new SIM card in the mail a Red Pocket Mobile customer support representative can help you switch your phone number over to the new wireless network.
If your device is GSM unlocked and you're using one of our CDMAS network SIM cards
Great news! You do not have to make changes to your device. Simply switch over to one of our remaining networks. Visit
redpocket.com/plans to purchase a SIM card on one of our other wireless networks (like the GSMT, GSMA, or CDMA-V network).
Once you've received your new SIM card in the mail, a Red Pocket Mobile customer support representative can help you switch your phone number over to the new wireless network.