Wall cracks and electric problems

i signed the happy letter on the 1st of March and moved in,on the 5th i got someone to come install burglars and whilst drilling the walls started to crack i mean if the house is build properly why did this happen?I then send a complained email to cosmo client services on the 7th March, today its the 16th and still no feedback from their site.On the 14th night main switch drop(yawa) mind you only lights and fridge were on,reason for this unkbown. 15th we plugged iron to iron and switch dropped again burning iron.Now im stuck not knowing where should i go to get help