Foschini complaint about a phone

I bought a phone at foschini huiwei y6 2018 I was surprised when I got this phone they had to charge it first because it was battery low.OKAY!! When I got home I charged my phone and then it was on 100% after 5minutes the phone was on 16% that's when I realized this phone has a battery problem the next day I took the phone to the shop mind you it hasn't been 7 days yet it's still day 4 when I got to the shop I told them the problem of the phone they took it and told me it has to be checked after 2 days I received a message stating that they phone went for repairs I want to know how?am I not supposed to receive a new phone?the contract says within 7 days if the phone gives me a problem I will get a new one... today I went to the store to ask and I was told to wait for 2 weeks... please attend to my complaint