Advice on how to handle a "contract" dispute/bogus collections from landscaper

So my wife decided we should get some landscaping done. She contacted a bunch of companies to do estimates. She found one she liked and they emailed her the estimate. They included a link that said by clicking this link, you are accepting the work. She clicked the link.

She then sent them an email asking for a date and time when they could start. They responded that "We work in chronological order from the date deposit was made and will not set a time or order plants until that time". It also states on their website that they will not do a thing until they have received a deposit.

My wife was not happy with this answer, so the very next day, she sent them an email stating she was going with a different company that would give her a date in advance.

The next day (yesterday), she gets an angry voicemail from the owner stating that we have a contract in place (clicking a link?) and that he has already ordered the plants, and that he is sending the deposit amount to collections.

We then got a call from a collections company a few minutes later. I spoke with them and told them I would be disputing this collections bill.

How would you handle this? How could they possible win on this issue? They clearly state that they will not do a thing until a deposit is made, and as far as I am concerned, there is no valid contract.

I'm willing to fight this on general principle as opposed to paying them the $500.00 they are requesting.