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I can not transfer contacts from Sony Ericsson Xperia Mini (ST15i) to another Sony Xperia XZ1 (G8342) phone. Xperia Companion does not support my old phone.
Can you sync to your google account and import from there?
Hi @DemiGold, welcome to our forum!
Xperia Mini has reached it's end of support so I don't have access to the Support documentation, but as @ezy3 wrote, I think you are able to synchronize the contacts with your Google account, or that you can create a vcard (.vcf) file inside the contacts application that you can move to your new device and then import it (may need to use a SD card).
Tap the 4 lines in the bottom right when you are inside the contacts application and see if such an option is availabe to you.
When you have transferred the file over to your Xperia XZ1, open up the contacts application and tap the three lines in the top left corner > Settings > Import > SD card > select the file and choose where to store them (I would recommend your Google account).
I hope that helps! 
ezy3, thanks for the advice. But my old phone can't sync contacts with google account.
Jonas, thanks for the support. However, the import and export of contacts Xperia Mini does not support. For Xperia XZ1 this option is available.
Hi again @DemiGold!
I don't have a Xperia Mini at hand, but if you open up the Contacts application and then tap the bottom left button (the one with 4 small squares), is there any option available here to import/export? I'm fairly sure it should be available, but it was a while I had a look in that kind of device.
Sorry for writing bottom right in my previous reply, I confused it for another device.