Mobicell Q10 phone is the worst distaster

my Mobicel Q10 that i bought at Ackermans keeps switching off . Even when the battery is not low. I was using goggle maps cause i didnt know the area and it kept switching off, it was so scary cause i had to keep asking people for directions. Ackermans says i must leave the phone for 21 days. They do not reimburse cash or give another phone. and i need my phone.. I have never experienced this with all the other phones iv owned. This is really disgusting. and i feel that this phone is faulty. I would be glad if Mobicell can get i touch with me so we can resolve this problem