Swelling battery

Hello Peter, <br> <br> Earlier this year (Feb-March) I purchased a Samsung Trend Plus cellphone, MODEL: GT-S7580. <br> Ever since I had been having issues with the battery life, it has never for one full day, regardless of the fact that I use the phone or not. Recently the situation has deteriorated, the battery is swollen and it literally gets flat in less than two hours after being fully charged. Once it hits 60% it literally counts down to low battery then shuts down within 5 minutes. <br> <br> I would like to know what can I do to get help as I believe the phone is still under warranty. I purchased it at Foschini stores in Maponya Mall Soweto, it was a cash purchase. I still have all the paper work, receipts and all. <br> <br> Thanks, <br> Luyanda