"Ass Dialing" is something usually achieved by people with very large, very talented asses who wear cell phones on belt clips. When they sit on their phones, random button presses result in random calls all over the world. The recipient of these calls hears nothing but a stream of DTMF button tones and muffled conversation.
I have found it helpful to do the stretching exercises my physical therapist recommends. Do some core strengthening exercises, such as the ones highlighted at The Mayo Clinic. By keeping your core strong, your back won't put itself in a position to cause that sciatica pain you are having.