I would write a letter with very specific dates and numbers: the date you moved out, the 21-day grace period for them to return the deposit, the date you called them and they told you they would provide documentation as to why the deposit wasn't being returned, etc. Lay it all out, including that you didn't get a final walk-through. List every time you tried to contact first the original property manager and then them. List method of contact (phone, snail mail, email, etc.), date, and, where possible, time. Tell the entire story with as much detail as possible.
And then state clearly that the law says they must return your full deposit if they don't tell you why they aren't within 21 days, and tell them that if you don't receive the full payment of $3,000 by X date, you will take legal action and also contact the Better Business Bureau. If the law allows it, I'd include whatever extra costs you will take on, like legal fees, if they don't pony up NOW.
We were in a similar situation, where our landlords just didn't refund our deposit for too long a time. We did what I said above, and we received a check for the full amount that was postmarked the date I specified, so it arrived a couple of days after. The letter we wrote was clearly preparation for briefing a lawyer. We were dead serious, too; we would have hired a lawyer to get our money back.
Your property managers probably don't want to pay and are hoping that you'll just go away. Show them you're serious, organized, and prepared, and they might realize that trying to evade you won't work and isn't worth it.
Good luck.