Ok, at first I got the explanation and, having seen Sheng a few times, recognised all the detail he gave for verification.
However, I just started to wonder something...
...the new username is for anonymity because the detail of the negative review would let the SP know who he was, presumably by the detail of what happened.
...presumably the OP didn't want the SP then contacting him to kick off? (possibly he's thinking of some other consequence, but my point remains, I think.)
So, how is using a different name on here going to change ANY of that? As I see it, if the OP reads the review on here, she's going to recognise who it is, whatever username it's posted under and, if she has his contact details, they don't change just because the review is posted under a different name.
I'm guessing if he's that disappointed with the service then he's not going back, so it's not a case of not wanting to piss her off for next time.
The only way I can see this making any sense is if the SP was with an agency that the OP wants to continue to use and he doesn't want some sort of reputation.