Freightquote.com Invoiced later for triple original charges Lenexa, Kansas

I've used this company several times in the past year. Each time I used them I was sent another invoice for additional freight charges after the original amount due was paid. It was always a small amount and I saw it as a nuisance to dispute it and just paid it. But then this latest shipment of some foam pads to Hawaii from my warehouse in California. I gave the company the exact description, weight, and measurements. The quote came in at around $600. My customer agreed to these charges and I did also so I shipped them and paid the invoice as soon as I received it. Then, weeks later freight quote sent me another invoice for over $1,100 more. I exploded. I called my rep Tara and she said I should calm down and she would take care of it. That was a joke. Tonight I got an email from some sap in collections. I run a losing business and am currently in the process of going down in flames for the second time in 10 years. I have managed to keep my credit clean in all the mayhem so I am very defensive of my credit standing. I pity the fools at this fraudulent practicing company if they think they are going to go forward with this obvious fleecing of honest businessmen. My advice for everyone is to run away from doing business with this company of crooks.