Assuming you are confident you are in the right ... and ... neither the network or agency have been responsive ... and ... you promoted & adhered to any paid search policies.
Since you are not privvy to the contract set between a network and a merchant ... and the network is invoicing on your behalf, you might be able to claim against the network. In instances where I have been vociferous against networks a couple have suggested that we do not work with them anymore. Send a polite letter (recorded delivery) to the MD giving 14 days notice of your intentions saying that you will issue a small claims for settlement against the network, which is as cheap as chips to issue (circa £25).
Making a Claim
We recently had to reluctantly embark on a small claims against a network whereby the merchant was in the wrong, the network ended up agreeing to pay before it went to small claims, though I
am not sure if the merchant knows this, as I think it was unlikely the network wanted to tell the merchant they were in the wrong & they preferred to favour them rather than an affiliate. Which is fine that we got our due monies, but the principles of the network came into question.
If a network chooses to exclude you from programs, a foolhardy route, then simply communicate directly with the merchants on their network outlining your reasons & opinions of that network, even suggesting the merchant goes dual network. I don't think the merchants would appreciate it if the network intended to behave like that & prohibit the growth of their program because of the network's prejudices. It's useful to keep a database of merchant contact details. Most emails we get, if contact details are there, we store. If not it's easy enough to acquire with just a couple of telephone calls. A few networks don't like vociferous affiliates, those are ones we rank lowly. BBG's rarely engage on the forum or blogs (there maybe a pattern).
On a program information page, it should always say whether there is an agency & which one is involved (but it doesn't, with a few networks reluctant to still publish these), which will give an indicator to if they are on the white list & whether a network will be likely to bias with them. There a number of decent agencies around, but there are a few bad eggs.
Re Zed Media, I
am aware of a previous employee who worked there & a few months ago moved to i-level i.e. Next. I
am not sure which affiliate programs they look after but from their website clients include Powergen, Lloyds TSB, o2, Toyota, Scottish Widows, Hewlett Packard, Lexus, BT, Capital One, Tiscali, Sage, Staples, LOreal, Mini, World Vision, MBNA, Zurich, Saville Row, NSPCC, British Airways.
It's very useful to be proactive with the networks who guarantee payment and those are the ones we perhaps should illustrate more & bring to the fore. Some are just more helpful than others in resolutions, so let's beef them up.
Good luck with your claim, but be sure first of all.