Hi, Gabriel_Acunha. Have you checked if you have the latest software installed on your phone? To check, go to Settings> phone update. You may also try checking if the system app for audio is up to date. See this link: http://i.imgur.com/NtopD.png. If in case this steps do not work, you may try using the Windows Phone Recovery Tool. This may fix minor issues you are experiencing with your phone.
We'll wait for your reply. :)