There are times when an employer has a particular job or jobs that they are having problems getting people to do.  You may have been brought in to do job A but find out after you get there that you are doing job B that you did not sign up for.  This typically happens with a job that tells you that you will make a lot of money and when you take the job, you find that it is based on commission.  If this has happened, you may receive unemployment benefits.  You will have to prove that the reason you quit was because job A was much different than job B.  During your interview, tell Unemployment Personnel that your qualifications and experience clearly dictate another type of job Tell them that this is the reason why you left your job of five years and that had you know you were actually getting job b, you would have never left it.

Bring with you a copy of the ad you answered and any job description they may have given you.  You will need to also tell them about your conversations with the employer when you told them that this was not what you believed you were hired for.  What did they do to help the situation if anything?  Refer to the title of the job to help hit the point home that they are totally different.  If there is a salary difference based on this, explain that as well.  Tell the interviewer that someone else received a promotion and they decided to give you this job as you speculate as to what has happened.  You want to create the reasonable doubt in their mind.