Mnr

I bought a Vodafone tab 10' at the Kroonstad branch on 27/02/2018.It was working very well until a week ago,then whenever you want to connect to the internet it says:"no data connection". I was told by a cellphone technician that it must be the motherboard or the internal antenna and that it would cost more to repair than I paid for it. I contacted the manager at cash cash crusader and he told me there is nothing he can do about it.He said that you have one day after you buy it to return if there is any fault with it.But the technician told me it might have been a fault the tablet had when cash crusaders bought it second hand,and the problem only surfaced now. The receipt I got from them say you have a six month warranty on second hand products.But the stamp on the front say you have a seven day guarantee on the product.So what is my rights in this case?