Forget my previous post. I've checked my characters, and they're all sounding the same Irish (O'Hare) voice. I deleted them, and tried the same thing again and it worked until I changed character then changed back again. This glitch is really starting to get on my nerves!
Did you change your character through the character selection screen option from the customisation menu after already selecting a character from the initial prompt, or did this happen after you selected a character from the initial character selection prompt after pressing start and switching characters by signing out or turning of the profile or powering down the console?
I read over my post again and edited it to make it more clear, i'm starting to think It might be safer to
turn the console off before swapping characters at the initial prompt after the press start menu. I'm also suspect about the game's auto-save function because it seems to detect the last character played and set the focus upon that character so that next time you load the game that character will be selected (like a continue game function); so if it save this It might cause the glitch, thus it might be unavoidable
To be more clear on my part. The game starts with the press start menu, after that you are taken to the initial character selection screen, select a character and you get the three options to select, customise, or delete, after selecting the character, you got to the main menu, select the customise character and you get a sub menu with options to go and edit weapon attachments, clothes, and abilities. In this menu, at the bottom, is a option called "character selection"
If you use this option (as opposed to the initial prompt after pressing start) the glitch occurs, transposing your selected characters voice to all subsequently selected characters, and then reseting to a random new character voice upon restarting the console. So if this glitch happen on an initial load I'm afraid that their is pretty much no avoiding the glitch then

.
Though, come to think of it, I'm yet to test using a usb memory stick to save the character profiles. That way, if you create a character, you can atleast archive them to a memory stick as a backup, that way, if the glitch happens, you can rescue the character, and maybe the glitch will be corrected. Additionally, it would be advisable that players only put the character they want to play as on the hard-drive, so that way only 1 character is on their harddisk at a time, thus may prevent the corruption when moving between multiple characters.
I really hope this gets patched soon.