Southpaw1971:
First off, any kind of racism is unaccaptable and a professional driver of any standing in this day and age knows this. If I found myself at the wrong end of a vexatious accusation, here is what I would do:
Email (don’t call) them saying you take these accusations extremely seriously and wish to see the statements they collected about your alleged use of racist language (which, as a reputable company with a zero-tolerance to such behaviour, they would have conducted a thorough investigation and not relied on hearsay…would they?)
If they refuse, submit a freedom of information request
If they say they did not take written statements and relied on word of mouth corroboration, advise them that they are making a baseless allegation which amounts to slander and you will be taking legal advice.
And after they have stopped laughing, they will just ignore you IMHO