Service Tax payments

Dear Sir ,

My company is a service provider, it has not deposited service tax since 2007-08 due to some problem now they want to clear dues which is pending till date. However we had deposited some amount six month ago against 2007-08 & submit the return of particular year. but it was not correct amount(deposited) as per bank receiving. My querry is; can we deposit the difference amount of 2007-08 & can revise the return. what is the penalty will be created by the department. I am confused for 2007-08 matter and unable to take in process for next year (2008-09, 2009-10, 2010-11). Kindly suggest me.