Mumbai Custom Clearnance Help

Hi All, I am Indian, I am a resident of the UK. I have sent 'Personal Effects ' used clothes to my sister in Mumbai using the Parcel Force company. I declared the items cost £150. The parcel tracker shows that it has cleared customs and delivered at India Post Mumbai.

India Post (Bandra Post) office called my sister and asked for INR8500 to pay and collect the parcel. When my sister went to India Post (Bandra), the person said he had no bill against the payment to give her and would only accept payment in cash. This seems very suspicious to me due to the following reasons. Firstly, 'Personal Effect' items such as used clothes should have custom duty because the item is not for reselling. Secondly, if they are charging any fee, they should not hesitate to show the bill and accept payment by card.

 Can someone please help me to direct the right portal or contacts to enquire about the custom office?