Cellphone complaint

I bought a Hisense device from ackermans before 14 days the device did not switch on i brought back the device then they told me their going to repair that devise and i must wait for 21 days. after 21 days i went to collect that device and they gave me a new one. after some seven days the device did not switch on and i went for the second time they told me to wait for another 21 days. after 21 days i went for the collection it was not repaired because the sale consultant send the device to vodacom instead to mtn and they did not brought back my original slip. i asked for the manager to assist me with the problem he told me that they device should be booked again to mtn and to wait for another 21 days now i received a message from mtn that i should pay R1492.11 i have never use that devise since i bought it.