Can i refound this faulty router!?

I brought this faulty router within 7 days , then i bring back to the shop( Challenger) for full refound or exchang ( if exchange i would like to have the balance return me in cash ,they said not possible , only give me back balance voucher, i felt being force to shop there) , therefore i asking for a full refound due to the router faulty, they said receipt indicates no refound and no exchange, and this policy is not hightlight to me before i paid the money , i felt being abuse with contrac law. for my understanding , this "no refound "policy not only misleading and also not legal as it only indicate me after i paid the money which the trasaction already took place, i want sue them , please give advises. thanks

my number 91703237 phone advise are more welcome

really mad up with this , felt refound right being abused

[annjd]

It is under warranty right--so they must fix it.

Does that not resolve your issue?