You need to do APN settings on your device. Please refer to APN Setup page.
Please confirm the following:
1. All characters are in lowercase
2. There is no space in between, before, or after the characters in the APN values
3. The phone needs to be restarted after adding APN values.
For iPhone users:
If you have a currently installed APN profile, please delete it before setting up the new APN for our SIM card.
You can do that by going to Settings > General > Profile > Remove Profile.
Please make sure to type in the APN values for "Cellular Data", "LTE Setup", and "Personal Hotspot" to fully use the data service.
For Android users:
Please make sure that the APN profile is correctly created and saved. Then, please select the profile you have just created.
If you are using a dual-SIM device, please select the correct SIM slot for the network.