Shanghai to Guangzhou, Guangzhou to Vancouver

Hello.
I'm heading to Vancouver from Incheon(seoul, south Korea) via Shanghai and Guangzhou.
It's gonna be looooong journey, but I couldnt help myself booking this.

My journey would be like this :
1. Incheon - Shanghai
Stay over: 6h
2. Shanghai - Guangzhou
Stay over: 18h

And, here's my question. ;)
This journey will be more than 24h, therefore the airline service center told me to apply visa regardless of this 72-hour policy.
I thought very simple...
Should I get another entry permit although I'm gonna stay at Shanghai and Guangzhou less than 72h each.
Please save this unfortunate soul!
Xx