Composite supply - Goods and Services Tax - GST

Dear experts, Tax payer has two seperate concerns, one supplying CSD Beverages at 28% rate of tax 12% cess ( Total 40% of tax) and other concern providing transport facility to the first concern(only) at 12% rate of tax. Now Assessing officer questions the seperation of two businesses and alleges that the intention of the tax payer is to evade payment of tax at rate of 40% as composite supply. Kindly provide the following clarifications: 1. Whether the seperation of two businesses of the tax payer is not allowed under the Gst Act? 2.whether the supply has to be treated as two seperate ones or is it a composite supply and liable to be taxed at 40%? 3. Whether any case laws or Rulings were available to defend the case ? Thanks in advance for all experts for your immense support.