after effects frame rate changes but audio stays the same after rendering in media encoder

We need complete workflow details and render settings. Changing the frame rate in the Render Settings does not change the time it takes the video to play, it does not change the speed of the playback. Unless you are an expert in formats and video standards you should always use the presets that are included with the Media Encoder or the Output Module/Render Cue. If you are using one of the standard presets, and you are using one of the composition presets everything should match.