But there are things you can do to stop her, you can report her to the camsite. Most girls who do this get banned quickly. The OP also mentioned it being streamate, I am pretty sure there is a review system there. I understand that it is difficult to accept, but you've got to understand that as sex workers many of us have been scammed far more times than members on camsites. For every camgirl out there looking to scam people there seems to be about 20 dudes. Some of these guys are pretending to be camgirls preying on people on various social media platforms, and some of them are out there looking for sex workers to scam out of shows. But in these cases they don't do it because they're broke, they do it because they enjoy having power over others. It's not a male versus female thing, I think it's an anonymity thing. If you're a camgirl your face is directly linked with your profile, it's much easier to be a member who can simply change their username. It is all wrong and it shouldn't happen, but I guess if you face most work days with someone trying to scam you, you kind of develop a "it happens, move on" attitude.
And when it comes to men threatening to get "revenge" on anyone, especially a woman who appears in a vulnerable position, I lose all sympathy. I don't care if that just means you're going to try to get your money back, using the word revenge puts pretty horrific ideas in my mind. £350 is not worth the trouble. She has done wrong, yes, but at the end of the day, it's just money.
