Playback speed for IPhone3GS - where is it????

Hi all, I have a few Audiobooks which I listen to on my IPhone 3GS a lot and I put a couple more and last night I downloaded them and now they have an echo which it didnt before. From what i have read I need to change the playback speed but from all the feedback I have seen online there is no icon on my phone at the bottom right corner I can touch to change it. I have just about tried everything with no luck. PLEASE is there anyone that can help me. I have already lost these books once and have spent a lot of money getting them back. I will very angry if I cant listen to this now. Many thanks and I would appreciate any assitance.