Inconsistent Policy regarding faulty batteries

I have a Samsung S4 which I bought two years ago. I had a problem with the battery, which swells up and pushes the screen of the phone outwards. Earlier this year I took it to a Samsung store and received a replacement free of charge, which is in line with published statements from Samsung as they know that these batteries are faulty. This second battery has now also started giving the same problem. I took it to the Sandton City branch and was told the guarantee is only for a week and thus I need to buy a new battery, which I did, for R400. Very dismissive and unhelpful staff. I complained to Samsung and was told the warranty is 12 months, starting from the date of purchase of the phone. This makes no sense as the battery is a separate entity and I have had the second battery for less than 12 months so why is it not covered by warranty?? I was told this was being escalated but have not received a response as yet. Very inconsistent and poor service. I would like a refund for the new battery as it should have been replaced for free.