India Post — complaining regarding kolkata post

I would like to complaint regarding kolkata indian post which it takes so many weeks to hold delivery parcels to my place shillong. I used to buy items from china but after reaching kolkata post my item got stuck for like 3 weeks in kolkata post, i dont know whats services they have provided that every item it took that much to hold for many weeks, i think workers did not take seriously about there work. Others country it just took like a week or 12 days to reach and here in india, i just think may be other city is quick but kolkata post is horrible.. I ll attached my destination transit

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India, kolkata foreign lcao, record item customs information (Inb), air, ced kolkata, retention reason : awaiting presentation to customs commissioner

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India, kolkata foreign lcao, transfer from office of exchange (Inb), air, ced kolkata

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India, kolkata foreign lcao, receive item at office of exchange (Inb), air

[protected]:10
Singapore, singapore s05, send item abroad (Edi-received), air, kolkata airport sorting office