Battery Life of a new Hisense cellphone is ****

About a week ago, I bought a Hisense U962 model cellphone from Springs mall(Woolies) and was assured by the sales lady that the phone is the best in its market. As soon as I got home I put the phone onto a charger until the battery was on 100%. It was to my surprise that within an hour and without really doing much on the phone, the battery was below 50%. I thought this might be because its new but have since noted that the battery doesn't last even a day meaning I have to keep it on a charger to maximize use. A cellphone is suppose to be a mobile device and if the battery life is **** then how am I going to survive with this device? I need to have this battery replaced and assured that the new one will not be giving me these issues. It’s only been a week since I bought this phone but Im already having problems!!!!