Sony Xperia XZ1 Manual page 31

If the settings cannot be downloaded to your device, check the signal strength
of your mobile or Wi-Fi network connections. Move to an open location free
from obstructions or get close to a window and then try again.

You can manually add internet and messaging settings on your device at any time. If
necessary, contact your network operator for the required information.
To add internet and MMS settings
1. Find and tap Settings > Network & Internet > Mobile networks.
2. Select a SIM card.
3. Tap Access point names >
4. Tap Name and enter a name of your choice, then tap OK.
5. Tap APN and enter the access point name, then tap OK.
6. Enter all other required information. If you don't know what information is
required, contact your network operator for details.
7. When you're done, tap , then tap Save.

Check the signal strength in the status bar to make sure your device is connected to a
network. If the signal is weak or you have no signal, move to an open location free from
obstructions, or get close to a window.

Check the device memory to see if memory is available. If the memory is full, remove
messages to free up space.
To view the memory status
Find and tap Settings > Storage.
o
To delete a message
2. Find and tap
3. Tap the conversation containing the message you want to delete.
4. Long press the message you want to delete, then tap
.
.
> Delete.