Quad Electronics, the contract manufacturer of world's cheapest tablet Aakash, said on Monday it has not been paid for its work by the tablet maker, Datawind. Quad alleged that the letter of credit issued by Datawind was dishonoured and it has not received any payment for its work. Datawind CEO Suneet Singh Tuli had yesterday claimed that his company has cleared all the payments that was due to Quad, except except for the 600 units that remain unpaid by IIT- Rajasthan.