Reading these crack me up. Unishippers, like any other 3pl, simply sell a contracted rates with the carriers.
Some customers just aren't aware of how shipping tariffs work and think everyone is trying to hustle them when in actuality they never package or class things correctly. Don't buy the contract with the carrier if you don't trust the carrier, pick another carrier we have a contract rate with!
Carriers are also at capacity.
I would recommend paying more to go with a premier carrier now that they can afford to yank people around. Unless you're Walmart, or a major manufacturer, guys like Central Transport could care less about your one pallet.