No .... Ameritrade will definitely not call you first .......
I can only speak from my personal experience. My trading style has changed significantly but at one point I was almost always at my max day trading margin limits. 4 different times TDA called my cell phone for margin calls - twice I answered and dealt with it - twice it went to voice mail (once at 7:15PM) and both of those times TDA "dealt with it" for me. Your mileage may vary.