Where are some of the biggest freely available English 1 on 1 conversation corpuses that are in plain text preferably?

Question

I'm looking for a free, preferably plain text, 1 on 1 English casual conversation (such as texting back and forth) corpus that requires little to no preprocessing (finding and replacing characters). I don't want an audio transcription because it has a lot of characters to replace such as uh, um, tr- uh trash, etc. Any direction suggested that follows these requirements is much appreciated.