A couple agreed that when they want to have sex: they will say let's make a phone call.
1 day the man sent his son to tell the mum while she was busy in the kitchen, mum dad is asking you to come so he can make a phone call.
Mum says , go and tell your dad I am out of coverage area.
Dads says, tell your mum that if she does not come I will make the call elsewhere.
Mum says, go and tell your dad if he does that, I will open a call centre here.