

Refused to Travel on 72 or 144 hour visa free transit
I am UK Citizen, I was travelling yesterday 18/9/19 from London to Shenzhen via Frankfurt with return ticket from Hong Kong to London within 6 days. So, A=UK, B=China (Shenzhen), C=Hong Kong. Shenzhen is also a border of China & Hong Kong and its deemed as Land Immigration (it's like one just need to cross over the road). I was assured this is acceptable and hence I was allowed to travel from London LHR by immigration and airline staff.
However, at the time of connecting flight and boarding it from Frankfurt to Shenzhen (Air China), this so called flight supervisor who was also Chinese refused me to travel. She said I can't do that in Shenzhen and then after little discussion (one sided as she was not interested in what I had to say), she said I need a train booking from Shenzhen to HK, but she was not prepared to understand that Shenzhen is the end and there is no such thing. Only train is a like a subway and that too for couple of stops and it cannot be prebooked. It was unbelievable that threw my passport on my face and walked off. These Chinese are not aware of their own country's visa regulations and criteria.
Has anyone experience this and does anyone know what can be done now. My flight from London was Lufthansa and from Frankfurt it was Air China. Who is to be blamed here and what can I do?
Many Thanks.