Seek information from the director about the job in hand
Exchange information or ideas with the casting director or directors on what you have to do precisely. First of all, ask him what you are supposed to do at the auditions. In most auditions, no preparation is needed and usually actors are asked to read from a script or take part in improvisational situations. On the other hand, if the director tells you that you should be ready to read a monologue, then you cannot avoid this scenario. Try to be confident in the audition and you will most certainly do well.
Your Behaviour Should be Good
Talk to the man in charge and explain to him that you are not comfortable reading a monologue. Moreover, if you don’t want to read a monologue under any circumstance, ask the casting guy whether is it possible for you to prepare a small scene along with another actor. Tell the director that you wish to display your potential in the best possible way, and that would be best shown in a short scene. If he thinks you are making sense he will allow you to perform a scene, and that way you will avoid the monologue reading.
Prepare for the worst case scenario
Do not force your agenda and be ready if the director disregards your plea. As a professional actor, you require the acting job a lot more than the casting director needs you. He can easily find other actors who are desperate to work and also willing to read a monologue for auditions. If reading a monologue is a must for the audition and you cannot get out of it, then you have to read it to show your talent.