First, I apologize if this too subjective, but I don't know where else to ask.
To sum up, I am legally considered to be "self-employed". Officially, I am a contractor, employed by "Company A" to provide on-site support for customers of "Company B" (the work location is owned by "Company B", the equipment on-site is owned by their customers). The contract is "indefinite", meaning it does not end on a specific date. What this means, is I have somewhat reliable long-term employment with no benefits, no vacation, and I handle my own taxes (they are not deducted from my paychecks due to being "self-employed"). I have been in this position for roughly 10 months. The position is in the US, if it matters.
As of Friday afternoon, I received a phone call from a recruiter with an initial offer of a 6-month contract (with the possibility of permanent employment at the end of the contract) that I would like to take if they offer it (phone interview with the recruiters boss is scheduled for Monday). I don't know if I'm really qualified, but I was honest with my experience, so I figure it's their problem if I'm not. To that end, I don't know how to answer the inevitable "Why are you leaving your current employer?" with honesty, while also not bashing my employer. The short version of it is that basically everything that was described in the interview and job posting was a lie.
The long version is that the position was advertised as semi-technical, with a transfer to a more technical position after 6 months. Neither of which is true as of yet. The hiring manager (the closest thing I have to a "boss" with Company A) is also the CTO, and does not have time in his "very busy schedule" (their words, not mine) to schedule my 30 day, 90 day, OR 6 month review, which are required before they can put in for the raises that were promised as a condition of my accepting the position.
That said, I have no significant issues with my co-workers in our limited interaction (we are generally alone for our entire shift). I like my direct supervisor (who works for Company B, not Company A like me), and as far as I can tell, he likes me. I have no problem with the position itself (in fact, I'm already paid significantly more than my co-workers, as far as I can tell). The problem is the position was "significantly not as advertised", the employer is dishonest, and is not what I am looking for in a career.
How can I answer the question with honesty, but also without sounding like I'm a terrible employee and/or bashing the company to make them look bad? "I am pursuing better career options" just comes off as being entirely too generic. What's to stop me from "pursuing better career options" in another 10 months if they hire me?