Damaged Phone

On 28 November 2015, I bought a Sony Xperia Aqua M4 cell phone from Vodashop Ilanga Mall. I bought the phone cash R5299. I was then asked to sign an agreement on the T?&C's. On questioning the sales person, she informed me that the agreement stipulates that if the phone were to be faulty, I need to return it within 7 days to get a new phone, after that it will be sent in for repairs. I took possession of the phone, and at home, when I tried to charge the phone, it was faulty and did not charge the battery. I then took the phone back on 30 November. I was then informed by a different sales person, that I had signed an agreement stating that the phone will be evaluated for 7 days, only after which it will be decided to either repair the phone or to supply me with a new phone. How can it be the consumer's fault if a faulty product was sold to him? He then stated that I should have tested the phone in the shop before leaving. This policy is extremely unfair. I was misled when signing the T's&C's, believing that I am protected since any faulty phone can be returned within 7 days. I will be leaving the country on 16 Dec for two years, and need the phone urgently! I can't wait for repair