Getting overcharged for Plusnet Unlimited broadband.

[#1]

Hello all
I signed up for unlimited broadband and evening/weekend calls. In the email I received it is listed as "Plusnet Unlimited (Contracted)
12 month contract (Unlimited usage allowance)".
In the same email I am told that "As you've signed up with a special offer, your monthly payment will be: £2.75 for the next 12 months". I paid the line rental up front. When I inspect the bill to be paid in early January, I see I am in fact making a payment of "9.99. I cannot find a clear reason for this. The breakdown of costs states that I am paying for "Plusnet Unlimited (Contracted) - Market 2/3 charge". I see this as a bit of obvious obfuscation on the part of Plusnet. What is a Market 2/3 Charge? None of this was ever made abundantly clear, or clear at all, upon signing up. As far as I can see this is a clear case of 'bait and switch', because I was promised a cheaper deal (the only reason I ever considered plusnet in the first place) to be hosed by higher costs. Burying caveats in walls of text, and using faux legalese to do so, seems fairly morally reprehensible if it turns out that this bizarre market charge was mentioned in the supporting documentation.
Just now I got off the phone having spent an hour trying to get through to an 'adviser'. No luck, even after a solid hour of '80s hits in my left ear. What can I do at this point?

[#2]

I'm not in the office at the moment, but I'll certainly take a look at your account tomorrow morning.
It's likely that, as your invoice hasn't been generated fully yet, that the discounts won't have been added to your bill yet. Discounts are added to your bill when the next invoice is generated. I'll double check this tomorrow for you though to ensure that the correct discounts have been applied to your account,
Apologies for the long call wait - we're working on this, we're hoping that you'll see an improvement in the New Year.

[#3]

I can answer the easy bit - Market 2/3 charge is because it is higher on Market 1
There should be a discount floating around somewhere but it looks as though something has glitched

[#4]

Hello Chris.
I think I was told, via the medium of pre-recorded messages, that you are opening up a second call center? I don't think I can cop the right accent, otherwise I would give it a bash.  
I received an email today notifying me of the payment in January.
To quote the email;

Quote

Account username: (redacted) Company name: N/A We'll soon be taking a payment of £17.26 for your service. This will leave your account on or after 02/01/2014. This email is sent for your information only, you don't need to do anything to complete the payment. Direct Debit Payment Details

This seems fairly final?
Also, where can I see a concise breakdown of these 'Market X' tiers?

[#5]

Ok apologies for double-posting.
Having looked at the bill again it appears that the discount has been applied, and that the bulk of the charges come from use of the phone. I think some people are slow to grasp 'evening and weekend calls' round here... 

[#6]

Ahh - I see, that makes sense then.
Here's some information on the Market Areas: http://www.plus.net/support/broadband/products/low_cost_areas.shtml
Yes, we've opened up a second site over at Leeds, it's a case of getting the new guys and girls trained up which should certainly help