qatar airways confirmed booking cancelled without my consent

i have booked an online ticket with qatar airways ref no 38GKIF but after 3days i have got a phone call from qatar airways saying that my booking is cancelled because there was some technical error on their system and in return they offer me a 50% discount on fresh booking i agree to them and now they email me with new booking price which is 951£ as offer but the same fare is showing on their current site (qatar airways) SO where is your promise gone ,this is like playing hide &seeek with the clients ,how can a an award winning airline do this types of things with their clients .also they tried to break the law by cancelling the ticket without my consent ,but now our law in u.k is geeting weaker and weaker day by day like cancer