HT4623 my phone iphone 3 it not have feauture to update software which has make most items such as camera ringer and some other features not functioning again.please how get it fixed

Good day,

I have an ipone 3 model MB702LL  with serial number 839144TAY7H.I have encountering problem with it since i bought it,it does not have the software update features with had make it difficult for me to download or update some software.Anytime i want to download software from apple store it will say the ipone is not compatible or needs an ios update.At present the camera,ringer and speaker is not functioning.

please how do i get it fixed because am not enjoying the feactures of using an apple product.I shall look forward for your soonest and possible reply.

Akeem