Bad service and clue less about their return policy

I bought a phone Mobicel R-1 on 23rd sep 17 Ackerman's Chrishani mall, the phone keeps freezing and mixing colors randomly about twice daily since the 25th. On the 29th I took it to Sandton Ackerman's as weekdays am working that side and was advised they cant exchange it since its IME number is registered with Chrishani store, they then advised Chrishani will be able to take it back today 30th. Chrishani branch manager Thomas or T-manager refused to take it back claiming 7 days is over, Sandton store should have phoned his store of this matter yesterday. He then proceeded to make further claims that am lying the phone is working 100% after I have told him, I just did a phone reset and it freezes randomly. I am irritated when stores don't abide to their return goods policy and take it further to pass the buck this one should have done this and that as if they are the ones using the products daily. Unsatisfied Mpho