Standard Chartered Bank — unethical late and interest charges for emi - scb credit card

All of a sudden they created an Instabuys card account without my consent and started showing the transaction in both accounts.I had converted an amount in 3 EMIs andstarted getting Lae charges+additional interest charges despite of ontime payment.Moreover the funniest part is (a) you can't pay EMI using the Instabuys card number though are mentioning and refering to this account all the time (b) they expect you to call them after payment and intimate them that with your due permission they can transfer the amount from primary card account to Instabuys account.What a policy to iiritate customer.I had to pay the outstanding amount for 2nd EMI otherwise they will again impose the same late charges and addl interest.However the same story happened this time also.Payment is lying in my primary card account and the amount is still showing as due.I want justice and also the additional charges what they have imposed on me in unethical manner.I have already fed up with writing to them[customer care, Head-customer care and Country Retail Head] also.But all in vein.They are blackmailing the customers in this way.