Hologram SIMs are designed for global IoT communication and are generally considered to be non-domestic devices by local carriers. This can be an issue when it comes to delivering Short Message Service (SMS) messages.
SMS messages sent from a Hologram device marked as delivered indicates that Hologram has delivered the SMS message to the receiving device's network. However, this does not guarantee that the receiving network will successfully deliver the SMS message to the end-device.
Similarly, SMS messages sent to a Hologram device marked as delivered indicates the sender's network has delivered the SMS message to the receiving device's network (the network the device is connected to, not Hologram). Again, this does not guarantee that the receiving network will successfully deliver the SMS message to the end-device.
Please note that Hologram charges for attempt of delivery. If Hologram successfully sent the SMS messages, the SMS charge will be incurred even if the end device does not receive the SMS message.
Common and Known Issues Related to SMS Delivery
Some carriers block SMS messages from international networks by default.
If you are sending SMS messages from a Hologram device to a cellphone, you should first try reaching out to your local carrier and confirm that the cellphone can receive SMS messages from +882 phone numbers. The outbox number for SMS messages will always be from a +882 number. This is true even if you purchased a phone number.
SMS on Cat-M1 is not yet fully supported by all networks.
This is usually due to timing issues related to the longer sleep duration on newer power efficient networks like Cat-M1. We expect these to improve with time, but it is hard to give a timeline given that these are network maturity issues that each carrier addresses as they see fit.
We have also observed that for some Cat-M1 networks, both the sending and receiving devices must be connected to the same Cat-M1 network for the SMS messages to be delivered.
Cat-M1 is an IoT-specific radio access technology designed for the Internet of Things. Carriers' focus is on improving the packet-switched (data/Internet) issues on the network before focusing on the circuit-switched (SMS) issues.
Networks have incorrectly mapped and configured Short Message Service Center (SMSC) routing.
SMS delivery relies on the assumption that every network has correctly mapped and configured the Short Message Service Center (SMSC) routing. This assumption is not always true. If the mapping and configuration is incorrect for one of the networks involved, then SMS messages will not always reach their destination. Both the network your Hologram device is connected to and the network of the receiving device must be mapped and configured properly. Individual carriers manage their mapping, so Hologram cannot update these configurations.
Additional Troubleshooting Steps
- Check the Hologram status page to confirm there are no open issues affecting the REST API or SMS.
- Confirm both the sending and receiving devices are powered on and have adequate signal.
- If sending an SMS message from a Hologram device, confirm the receiving device can receive SMS messages from non-Hologram devices.
- If sending an SMS message from a Hologram device, test with a different device on the same carrier as the receiving device. Confirm that the second device can receive Hologram SMS messages.