Havent received deposit balance, past 21 days post move out (apartment, lease)

[calrenter]

Hi,

I moved out of my old apartment on 18th Feb. I lived there for 2 years with family (wife + kid). I did not do any cleaning as such as I thought it was relatively clean for having lived there 2 years. I received an itemized bill of costs for repair from the manager.
The cost was going over 500$, which was the deposit amount, and it showed that I owed them money. Major chunk was paint material and labor. But the manager had calculated based on 1 year lease, which was wrong. I pointed out that I lived there for 2 years and asked her to recalculate it. I said that the paint charges were too high, but couldnt really argue on that. She sent me a recalculated estimate but the figure again was totally wrong and I couldnt understand how she calculated it. I sent her a reply with all the calculation in detail as per their itemized statement and correct lease term for paint cost calculation. By my calculation which I am pretty sure is correct, they owe me around 16$. She replied at around 4PM that she would have to respond to me regarding this the next day. I havent heard back from her since. This was around 9th March. It has been more that 21 days after I moved out. The amount they owe me from the deposit is not big, but these landlords fine us 75$ for delaying rent for 3 days. Why should we let go of our money? Also should I expect interest on the deposit?
I was thinking of getting in touch with somebody higher up in the company tht manages that community.
What should be my ideal next step?

thanks
calrenter