Tax rate calculations incase non submission of c form

I have done some CST sales against the c form condition with the buyer. As per then law of the state I had paid purchase tax on the goods purchased. A that time the purchase tax was 4% and the CST was also 4% . But latter unfortunatley few of my buyers failed to provide me c form due to closer of their business.. Now my local sales tax office demanding the c form and even served notices for attachment of my bank account. I have paid our state's tax and sold against the buyer's cst waybill. It is also confirmed that my buyer has paid the tax in his state and reflected the transactions in their return. The department of Sales tax has sent me a notice to pay the tax amount on balance due of C form @ rate of 8% . And after the complaining the higher authority has reduced the tax to @ 4% on the balance amount of the C form transactions. Now my queries on two following points : I) where as I had already paid the tax while purchasing the goods to the originating state then how can the same state will collect the tax again on the goods. That’s mean the double taxation on the same goods. Once I had paid @ 4% tax while purchasing and again pay tax @4% towards CST. ii) Secondly, in some cases the department collects the state sales tax when the dealer failed to provide the C form. The usual practice is that the department calculates the amount of tax as per the state’s tax rate and adjust the amount already paid towards the CST. The dealer has to pay the deference amount. In most of the cases the CST rate of tax is much lower than the state’s rate of tax. But I my case both the State’s rate of tax and the CST rate of tax i.e. 4% is same. Then how much the tax I should pay towards the CST now. I had raised the issue with some advocates but unfortunately got difference of opinion. I heard about this Lawyers Club India Forum. I will be highly obliged to get the proper guidance in regards to the afro said matter from the best mind of the trade. Thanking you and with Warm Regards