Godrej Modular Kitchen — Modular kitchen Payment and invoice of materials

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Thane

Why a costomer do complete payment for modular kitchen before installation, As there is no trust that the job will be completed or not, Installation charges are seperate so advance cheque should be taken so stop payment can be done if installations not done or any dispute, why original invoice of materials from Godrej with price not given to customer, why compensation not given for delay in work.
Where a customer should go if the work is not done after giving complete payment as shown in review.