BooksButterfly, you're sinking your own ship.
Yes, you're entitled to defend yourself when faced with unjust accusations. Or even just ones. However, you really should ask yourself first if it's in your interests to do so.
If someone buys your services then doesn't like them for whatever reason, your priority should be to work out a resolution that customer is happy with. Because then that customer might well return to the negative reviews he or she has left and announce that actually, you're great to work with and have gone out of your way to be helpful.
If instead you follow your disgruntled customers around the internet and throw out accusations of defamation, you just make yourself look like a banana.
I can guarantee that your responses in this thread have done more to lose you customers than the post you found so objectionable.
If instead you'd come here, admitted that mistakes had been made, and fallen over yourself to put those mistakes right, everyone would have appreciated it and would have cheered you on.
Instead, you've not only further alienated someone who was your customer, you've also put off lots of other potential customers.
You can learn from this if you want to. Or you can carry on with your long posts, and your outrage and justifications, and destroy the business you've worked so hard to establish so far. It's up to you.