Sony Xperia XZ1 Manual page 32

To delete conversations
5. Find and tap
6. Touch and hold the conversation that you want to delete.
7. Mark the checkbox for the conversation or conversations that you want to
delete, then tap

Check that the MMS auto download function is enabled in your messaging settings.
To enable MMS auto download
0. Find and tap
1. Tap , then tap Settings > Advanced.
2. Drag the slider beside Auto-download MMS to the right.

Use the full number when you send a message. When you enter the country code, use
"+" instead of "00".

Turn off your device and then turn it back on. By doing this you turn off all running
applications and free up memory, which sometimes automatically solves the issue.

Update your device to ensure that you have optimal performance and the latest
enhancements.
I cannot connect to another device using NFC
Xperia™ XZ1 Dual SIM support overview

Make sure that NFC is activated on both devices.
To enable or disable the NFC function
1. Find and tap Settings > Device connection.
2. Tap the NFC slider.

Make sure that the screen of your Xperia™ device is unlocked and active.
.
> Delete.
.
Read about how to update and find latest software version.