I have a contract with blu connect of a cellphone

I have a contract with blu connect of a cellphone. The device was delivered but it was faulty. So I informed them January this year,the courier came to fetch it for repairs towards the end of January,only to be informed that the phone is irreparable. Now the asked me to pay R1800 so that they can send me a new device,of which I told them I don't have that amount of money.They keep on deducting R449 but I don't have the device with me.