If you had booked a punt with a WG and then notice that the price has increased would you just pay it, it’s £20 by the way, or would you argue for the price you booked it at?
Firstly, well done for spotting because it's easy not to then check and one could be faced with an awkward situation. Some guys would just wing it, go there and argue their case but that does rather risk a standoff and a bad start to the punt or wasting your time.
To avoid that, my advice would be contact her in advance and clarify you assume you will pay the price you booked at. If she refuses, then you have a choice to make: do you think she is worth the extra £20 and still want to go ahead on principle. Up to you.
I booked one WG in the morning when her profile said £90hh then when I got there she asked for £95, saying she'd just changed it, without really backing down. As it wasn't much and I had the fiver I paid, plus she was hot and I wanted a shag, I just paid it. Fortunately it was a good punt.