I had the the no sound issue also on my iPhone. I found this trick to solve the problem and it give back all sound on any iPhone.
1- Go to Settings
2- General
3- Scroll down to : Accessibility
4- Select Assistive touch (for more information about Using AssistiveTouch on your iOS device : http://support.apple.com/kb/HT5587)
5- If the "White dot" doesn't appear - Click 3 times to the home bottom and you should get the "White dot" somewhere on your iPhone sceen (you can move the "White dot" where you want on the screen of the iPhone)
6- When you get the "White dot" - click on it
7- You will have 4 icons, click on the device icon
8- Click volume up (be sure the volume is at the maximum)
9- Click on the little bell (make sure the bell is not muted - I found, it's not very clear whic bell is on or wich bell is mute)
10- Call your iPhone - the problem of no sound should be fix (if the problem is not not fix be sure the volume is up and the bell is not muted - select the other bell by clicking on the bell - call again your iPhone - the problem should be solve and it should work)
11- If you do not like to keep the "White dot" on your iPhone screen - click 3 times to the home bottom and the "White dot" should disappear (if you want it back - click 3 times to the home bottom and the "White dot" should be back)
I found this trick at : http://www.iphonefaq.org/archives/972122 - My iPhone ring/silent switch is stuck on mute, how can I turn on sound? - On the comments of " hi iphone users i have had " Submitted by jodray (on February 5, 2013 - 10:05am.
Hoping it will work for you. Best regards.
