How long does it take to get a billing question answered?

[#1]

Recently extend my contract with Plusnet and a question had been posted by the customer services team outlining the the new contract details.
A week later I then received a new month invoice later with the incorrect charges and the money was taken of my account via direct debit! 
I responded to the question earlier this week, but have still not had a response after 4 days.
How long does it take to get a response to this billing query?

[#2]

I don't know but mine wasn't picked up until I posted here http://community.plus.net/forum/index.php/topic,142191.0.html

[#3]

I've looked at your bill and I can't see any issues.
If you look near the bottom you can see your special offer discount which is the discount for your broadband.