Warning - Cheaters on People's Square (Shanghai)

People's Square -> Tea House

Tea story - Peoples Square

It wasn't the first time when some girls in People's Park (People's Square) in Shanghai asked me to take a photo of them.. and then ... short chat..
They usually say they are from other city, visiting Shanghai, walking around to sightseeing. Two times before after that short chat they also offer to go and see with them a tea house (I thought it is nothing strange - people in my country are nice and sometimes they offer you short trip around to show the city). Before I always deny because I was in a hurry.
But today I thought - why not all those people goes there so it might be interesting. So I went there with 2 Chinesse Girls (the place they took me is called "Champs-Elysées" and it is behind CapitaLand next to People Square. So the most interesting of that story was especially on the end - Protected content to pay - for tastying 6 kinds of tea and one can of tea. They asked me to split the bill into two because one of them pretend to be 19 years old - so they said she is young and doesn't work. I disagree.I feelt that they are cheating on me so I asked them why it wais so expensive and to detail the bill. But finally I didn't know what to do so we split it on Protected content they ask me for Protected content . I paid it - so I get a can of tea and I went out from there. Of course the girls still try to be friends an even walk me a little bit in my direction.
After they left me I walked around and went back so see if they are on the same place when I met them before - of course they were there. Just after they saw me one of them told me that she is going to the toilet nearbay. I get very angry so and call my boyfriend to tell him the story and I decided to go back to this tea house. I think they may be following me because in the moment when I just got there the laidy was trying to close the door with big door loocker - but I was very fast and I get in before that.
So.. I shout at them, telling them that I will go to police if the don't give me money back, that they are cheaters and so on.. Finaly I got back Protected content back (they show me the menu for tastying Protected content for teasting one kind of tea plus 30 rmb for private room). Since today I won't speak with any stranger in this city. I know it was silly but - I wanted to get to know Chinesse culture - and I did..
Please share the story with any people coming to Shanghai.
Anyway do you know if anyone tried to contact the police in that case?