Oppo f1s(old) is one of the best phone for ever, in using it from last 5 month, its never get hang or any problem to operate. But there is no video calling option throw device, for video calling I have to use third party software, it should be inbuilt, battery backup is also good, but after 2month the charger stopped charging.
its bad to hear that after one month of purchasing this phone oppo launch same model in good configuration(4GB, 64GB)