Try to give them as much notice as possible and cancel the appoinment if you are nervous....... The provider would rather you cancel than be a no show & you will be happy that you aren't taking a chance getting ripped off

I justed ended up emailing with a cancellation notice as DB had mentioned... just wasn't sure if the fact I had come across a bad review was something I should mention or not...

process.  If you find only one TER review & it says ripoff, run away!  You say you are new, you need to establish some selection standards & stick to them.  May include age, hair color, etc., but has to include quality/safety factors based on reviews, like at least X TER reviews, average scores of X, no score lower than X.  It should never take more than one 'ripoff' review to make you look elsewhere.  Let's face it, there are so many choices in the DC area, there's always an alternative.  And as a self-admitted Newbie, you shouldn't TOFTT until you've got much more experience.
So bottom line, don't do this again!