Assuming it is as you say it is:
Get legal advice about possible damages or losses incurred as a result of your frayed nerves and wasted time! And see if you can get your legal fees back. Also, make sure any information they have passed to a credit agency or debt collector is rescinded at their expense, when you win, and you'll need written evidence to ensure this has been done (else you will have bad credit for years to come).
If everything is in writing - and make sure you collate everything carefully with your solicitor - a court will likely sort it out in your favour in minutes. Courts don't care at all about the "he said - she said" nonsense. Contracts, facts and dates are the key. A reasonable legal rebuttal by letter from your solicitor might make these people go away before it gets to court. Remember, their solicitor has only heard one side of the story.
The moral of the tale is that this company have probably already lost a few sales by showing poor service, so if in a hole... etc... They sound like a company that is a bit desperate in my view.
The plural of anecdotes is not data. Anecdotes however, are better than hearsay.
2014 Nav V6 (quite nice for a pickup truck) & Celtic Rambler (awesome as a mobile luxury flat).