Game cellphone not honouring 7 days return

I bought a cellphone vodacom vivo on 18th Feb 2020, and experienced phone freezing on the first day. I thought it because it was the first day with an unknown phone. As days progressed i experience more issues could make or receive calls. I then return the phone to the store on the 23rd Feb 2020. I was told that they need ro book this new cellphone for assessment repairs on it day 6 counting the day of purchase cause they will not give me a phone or my refund. I am very disappointed thati returned a defective phone and was told of up to 21 days without a cellphone while the store had my money. I use phone for business and it unfair that i am told that they need to keep the phone while they assess That means the phone is no longer new at all. The manager Simon even boldly said he will offerme nothing except assessment bt the 7 daye hasnt lapsed and even showed him the calls i coulnt pick now. I am stuck with a worthless new cellphone that i cant trust All i wanted was my money and purchase a new phone that will work for me.it sad that we told to return defective items within 7 days than we return we told that once it out of the door is assessment and repairs bt the item is new. What pathetic service Wouldnt advise anyone to buy a cellphone from such institution