Service Tax on advertising agent service - Service Tax

The department has issued Multiple Show Cause Notice to a client in the matter of service tax from advertising agency service. One show cause notice for the period 2008-09 to 2011-12 amounting to Rs. 79 Lacs was issued in 2013 by the Additional/Joint Commissioner, another show cause notice for the period 2008-09 to 2013-14 amounting to Rs. 8 crore was issued in 2015 by the Commissioner and the third one for the period 2014-15 amounting to Rs. 1.04 Crore was issued in 2017 to the same client on same matter. The client/noticee during the period 2008-09 to 2014-15 was engaged in providing taxable services as Advertising agency. They noticee claim that only 15% of the consideration amount is given to them as commission while rest amount was given to the print media by the recipient hence service tax is applicable on only 15% of the consideration amount which they have received. But the department has issued notice taking whole amount of consideration as taxable value and computed service tax on that:- the queries are (i) Is single adjudication possible for all 03 show cause notice issued by the department for different period on similar issued to the similar person? (ii) whether the noticee is liable for tax only on 15% of the consideration amount received from the Print media as they claim or whole amount of consideration will come under the net of service tax? (iii) Incentives received by the noticee from different print media due to achieving target withing due time, will come under the purview of service tax? Please guide.