gaplayer's fix worked a second time. So even when my phone started playing up again, I re-ran the fix and it re-fixed.
Now there's a new firmware / software release - this may help as well?
Gaplayer's fix below for those that need:
THE FIX - FOR ME AT LEAST:
- Open the dialler and type *#0808# (it's normally *#2873# on other Samsung mobiles but it did not open the USBSettings app at all).
- As soon as you press the last '#', the USBSettings menu will appear with several bullet-point style options:
- I selected the last option, pressed 'Apply', exited, confirmed the setting stayed the same, pressed 'Apply' again and then pressed the 'REBOOT' button.
I've searched the whole Internet to find solution for this issue. Then I tried gaplayer27's solution above, but unfortunately it did NOT work for me. However I found a possible solution on this page under a Samsung S9 problem that worked for my A70 too. The steps are the following:
Go to Settings
Swipe down, press About phone
Press Software information
Then press Build number constanty to enter Developer mode
After this in Settings Developer options will appear right under About phone
Press Developer options
Searh for Default USB configuration, press it
Press Charge phone only
This work for me as well, so I hope it will work for you guys too.