Not enough funds in account for a direct debit overdrawn.?

So it turns out I got my EMA a little late, this meant that on Thursday I didn't have enough money in my account to cover a direct debit for my broadband. It is now a week later, my broadband is still on but the money still hasn't been taken out my account for and I haven't received a letter from my bank informing me that I was overdrawn can someone help me out here and explain to me what this all means. Also how much am I looking at being charged for being overdrawn my bank is Santander.