The competent body is the Consumer Protection Authority, which applies the law and receives and investigates complaints from consumers and associations (art. 43). The executive regulations set the deadline for responding to a complaint at a maximum of thirty days (art. 43). The Authority may not charge any fee for complaints received from consumers or for the actions it takes on them (art. 45).
Where a dispute arises over applying the law or your right to exchange the goods or recover their value, the matter is referred to the Authority to issue a binding decision; it may order exchange of the goods, or refund of their value at the purchase price plus the return calculated at the Central Bank's announced rate, or refund of the market value (art. 52). The Authority may direct the parties to have the product technically examined at an accredited laboratory (art. 53).
You may also use consumer protection associations, which receive complaints and work with the Authority to remove their causes (art. 62). You may obtain an official certificate of the complaint's outcome and copies of the relevant technical reports (art. 61).
This is general legal information, not legal advice. For advice on your specific situation, consult a lawyer licensed in Egypt.