I have a used iPhone 4 with 16GB of memory in it, running IOS 7.1.2. The problem with this iPhone is that the volume is really quiet whenever i'm playing music or making a call and setting the caller on the speaker.
The volume is currently at it's max (by tapping the buttons on the side).
Note: I haven't used the "broken" iPhone for this screenshot, this was just for showing what I did to increase the volume to the max.
I have tried rebooting the device a couple of times already, this didn't work.
What do (or can) I have to do to make the speaker play at a decent volume again? Do I have to replace it?