MTN CELLPHONE. WITH DEFAULTS

I purchase a PAYG phone from Woolworths at the Cresta shopping center.1 day later it did not work.I went for an exchange and purchase a different brand,7 days later it stopped working.When I went for an exchabge or refund,First the floor manager told me I was using the charger in incorrectly,When I explained that this is happening for the second time ans actually the sales paerson had warned me that they had problems with these phone(SARSHA).Then the store manager(KARABO),said they cannot exchage or refund as the 7 day warranty had expired,they cannot only take it for repairs which would take 14 working days,as a sales person I explained I cannot perform my work duties without a mobile phone and as SARSHA(sales person) had informed me prior as well as in front of him that the phones were faulty maybe he could take it up with their supplier and give me an exchange.His response was that their sales person(SARSHA)was expressing her own views not that of the company(WOOLWORTHS),and I then need to take up the issue with the stores supplier(MTN)if I want to get an exchange.Since I have been without a phone thus no means of my clients to communicate with me and still no calls from WOOLWORTHS,and he gave me the tlephone number at MTN to sort out the issue myself.