vat act andhra pradesh 2005

while transporting the goods from one place to another plase the commercial tax person was stopped our goods and detained the goods on the cause of under value of goods . i was argued that the goods what ever the rate contained in the bill is true and correct. and the commercialtax person allegated that the goods contained undervalued what are the defences i have to release my godds according to the use of apvat act or sales of goods act please give suggessions