Shop gave less weight or quantity than I paid for

What usually matters in this situation, and the papers to keep ready before you meet an advocate or free legal aid (call 15100).

Before anything elseShort weight and missing MRP details are complaints for the Legal Metrology department of your state.

Your situation

Next step The National Consumer Helpline (1915) settles many refunds without court.

Invoice, bill or order confirmation
The basic proof of the purchase. Where: Order history, email, shop bill.
Refund, return or cancellation policy
Sellers are expected to follow their stated policy. Where: Website, booking confirmation, invoice back.
Warranty card or warranty terms
Warranty claims depend on the period and terms. Where: Box, invoice, brand website.

Payment proof — Shows the amount and date.
Cash bill or receipt — Cash purchases need a bill.
The ad, listing, or terms as shown when you paid — Shows what you were told.
Photos or videos of the defect (and unboxing video if any) — Direct proof of the problem.
Tracking history and delivery status — Shows non-delivery or late delivery.
Cancellation confirmation — Shows the refund became due.
All complaint tickets, emails and replies — The refusal is usually the key document.
Make a written complaint to the seller and keep the reply — Creates a dated record.
National Consumer Helpline docket number — Shows you tried to resolve it.
Card dispute / chargeback request to your bank — An additional route for card payments.

Consumer complaints generally must be filed within two years of the problem arising. Forum depends on the amount claimed.

General information, not legal advice.