144 hours free transit rules

I am travelling to Vietnam but snd staying in Shanghai for 5 days then leaving Shanghai to Vietnam Also if I got 144 hours free transit can I book a hotel in Shanghai and explore the city then back to pudong airport to Vietnam ?.i call the embassy consulates China in Canada spoke to them regarding to 144 hours free transit in shanghai ,they told me to call China border custom service to make sure ,and they are not sure I can use 144 hours free transit in Shanghai ,why wouldn’t they know i am concern to be stuck at China airport I checked on the China embassy website for the free transit ..can you assure me I can use 144 hour free transit rules to explore Shanghai for 5 days and I don’t need sppky for tourist visa to go to shanghai ,does China border control has an email to ask question about this
Thanks