Toni Earbuds Faulty, shop refuses to exchange.

I bought a set of Toni Earbuds @ R350 from Vodacom 4u in Clearwater, upon getting home I charged them the whole night the case, then left it to charge the earbuds another couple of hours, however The 2 buds dont fully charge up, they get to a max of 40% bud1 and 80% bud2. I did press the case charging button to charge the buds while on the cable charger and off the cable charger. I tried another cable charger and am getting the same results. I went back to the shop and they refuse to change them out for another pair as the packaging is torn, there is no other way to open the packaging as its sealed packaging, You have to tear it to open it.