Goq, you don’t deserve to get yelled at and no you were not hired to take abuse for your boss! If that were in your job description I highly doubt you would have taken the job!
No one has the right to be nasty or abusive on the phone just as no one has the right to answer the phone and be nasty and abusive. We already covered these issues in a thread called phone etiquette. No matter what anyone says here, YOU ARE RIGHT. People who call in have no right to take out their frustrations on you. They do have a right to say they are upset and angry, and they do have an obligation to apologize if they get out of line with you, but in no way are you obligated to take any form of abuse from anyone.
Since you do work in a yeshiva, you might consider discussing with the Rosh or Rav what would be the most appropriate approach to take when this happens. Should you respond, should you put the caller on hold, should you give them a warning that you will hang up if they don’t cease the abuse and then follow through, should you just transfer them to his line to leave a message, etc. It is best to have a plan rather than fly by the seat of your pants. If you have a system in place, it will be easier for you to handle these types of calls more efficiently and you will not be effected by them so much because you will just practice the plan you have in place and not listen to the abuse.