Many customers like to cover all the bases. They may get a bunch of different auto shipping quotes, book with a couple different companies, and let the first truck to show up take the car. This is a really bad way to do things. Although getting multiple quotes is great, but when it comes to actually booking the shipment of your car, you should only use one company.
It takes time for brokers to find a carrier and schedule your transport, therefore double-booking (booking with more than one company) will set you back more than you bargained for. Also, shippers will actually cancel your entire order, leaving you without a company at all.
Booking with one company is the best thing to do, not just for your wallet, but for everyone involved. It cuts down on confusion and allows brokers to do their job to get you the best price with a reputable transport company.
Reminder: Do your homework! Make sure that you check the Better Business Bureau as well as other resources available on the internet.