What makes a transcript come out well or badly
Three things, and none of them is the accent. First is how far away the microphone was: a phone in the middle of a table picks up far more room noise than the same phone in front of the person talking, and that noise is what turns into invented words. Second is whether people talk over each other — when two voices land at once, no system, and no human, gets both.
Third is your own vocabulary. Company names, surnames and industry acronyms are what gets missed most, because they're exactly what appears nowhere except in your recording. Two minutes with the text editor fixes them, and that's where accuracy is really won — not by switching providers.