Just another SD card issue

[AC Question]

Same problem as a lot of other folk, i guess. Samsung J3. 3 weeks old. I inserted a new one of Samsung's own darn cards and.... nothing, nada. says there's space on my nice new card. Er, 14 gigs on a 16 gig card. Stupid or what? I can't mount or unmount the thing. Can't format it and my ancient PC doesn't have a card reader. Am I completely screwed here cos my service providers are as useful as a one-legged man at a butt kickin' party!!