Bad service

Bought a cellphone cash at Mr Price, Adderley street, Cape Town. The battery of the phone was faulty within 4 days of purchase. I returned to the store to replace the handset as promised on the day of purchase, just to find out that il only have my phone back in 3 days. Kindly explain your policy w.r.t cellphones, as not the store or the callcentre was able to assit because its not a contract. On top on that the cashiers at The Adderley store found it very amusing and resorted laughing at me with no assitance and refused to take the phone back.