Permanently deleting photos iphone 4s ios9.3.5

Several of the suggested solutions to this problem refer to the "recently deleted" tab on Camera and photos. This is not available on my phone with the most up to date ios 9.3.5 that can be used with the phone. I have deleted the photos on the phone and on my pc using the photo program but it has made not any difference to the amount of storage used by photos on the phone. I am able to delete other apps and podcasts etc to free up storage space but if I continue to use the camera the storage will soon be full. Have looked extensively online/forums etc but found no solution. Please help!