How to get a pocket PC

I don't mean a phone, I just want a computer that looks like a decent phone, can be used like a decent phone, but is built to be a decent notebook with Linux.

Hardware: to be used as computer, but can perform like a decent phone

Software: Linux, with a desktop environment

I'm not a native English speaker, so i want to be sure. Phones are built to be used as phones, I just want a pocket Linux computer that can perform as a phone.

Ubuntu touch and KDE mobile and similar are maybe a little too general. I don't want to change this device every 2 years, this is a computer.

Advice needed