According to me, All the Branches is likely to have saperate GST No. In GST regime The Place of Supply of Service matters. which impies the supply within the state. So CGST and SGST will be applicable.
Having Bank A/C with SBI in WB. for services locally charged by branch it charges CGST & SGST, but for netbanking transactions it is charging IGST. How to pass entry in tally because the GST no is of WB.