I seriously don't get you Amarbir. According to you, you say that Chiragh and his dad abused you even before they ordered you the config. But you could not do much at that time. WHY, Cause you were trying to make a sale. If i understand what you are trying to put here is that you are ready to accept abuses from a customer before he buys anything from you but not afterwords even if the product you supplied is faulty. I run a store myself and yes i do screw up at times but i never make a sale to a customer who is abusive to me(heck nobody till today has been) and i make sure i clear the mess which i create.
Bottom line you screwed up, And you accept it, If you had the courage to take the abuses before he bought anything be ready to take some more after you have sold a faulty product to someone. To be honest what i understand from your post is that they Chairagh and his dad came to your shop to buy the PC, his dad is a bit aggressive and you understood that before making a sale. You should have made sure that you didn't screw up in the first place, which you did but later instead of fixing the situation you are making excuses like abuses and aggressiveness etc. Also i fail to understand how in the hell did Chiragh got hold of your mother's mobile number during a course of a night cause by your logic you supplied him the PC at 8:00 in the evening when your shop was about to close down and in the morning when you woke up next day you had the filthy messages on your mother's mobile. Doesn't make sense does it.
My "advise" to you, clear up this mess. Period.