glcmcfc,
I hope you will you permit me to ask the question suggested by my legal training. What do you want now?
It's clear that you're unhappy with Zen's handling of the situation. Ultimately, you will have to resolve this with them directly - they are precluded by the Data Protection Act from discussing your account in a public forum in anything beyond the vaguest fashion. Whatever you can prove about Zen's alleged mishandling of the situation will do nothing to further your situation - it's not actionable in any way so long as it doesn't libel you (and even if it does, a libel action is notoriously expensive to pursue).
I'm not sure that every call will justify making notes on the account, especially if the call is essentially covering the same ground as already reported in the notes. If you have made a high number of calls, that's not necessarily a good thing - some companies have special teams for people who call frequently, who still attempt to resolve your issues but also keep you away from other parts of the business so that they can get on with their work (e.g.
Vodafone's high caller department).
My reading of the situation from the outside is that the evidence Zen hold about your reported instability and speed issues does not cross the threshold to be reported to BT as a fault. If you want BT to be involved, you have to work with Zen to justify BT's involvement and you may have to take the risk of a 'no fault found' charge from BT. If you are not prepared to work with Zen on this in a systematic fashion - even if, to you, it feels like jumping through hoops - you will not get a visit from a BT engineer. Even if you can put together a good case with Zen's help, you may not get a visit. Sending an engineer is not always in Zen's gift, and if an engineer visits, there is only so much he or she can do. I suggest that you review clauses 12.3 and 12.4 of
Zen's ADSL and SDSL terms and conditions.
As I said in my earlier reply, it seems that Zen can do very little to make you happy now. You have very little leverage over Zen, as there is little you can rely on contractually and the monthly income from one ADSL account doesn't justify Zen making superhuman efforts to retain you. If you had a couple of leased lines and a 200 extension VoIP setup, Zen might be able to justify expending more effort on your account. Ultimately, if Zen feel that your continuing business is not worth their while bearing in mind the support resources you are consuming, they can give you notice equivalent to the minimum notice period (30 days on an ADSL product - clause 11.3a of
Zen's ADSL and SDSL terms and conditions) that they will terminate your account without liability to you (clause 11.7 of the
Zen general terms and conditions)
There's no Service Level Agreement guaranteeing a certain speed or uptime for a DSL product. If your line remains above the Fault Threshold Rate and there is no clear evidence of repeated loss of sync, there's little Zen can do. I'm sure Zen wouldn't want to give you notice of termination, but they may feel they have no option if you keep consuming a great deal of support resources without making progress.
If you want the collective wisdom of the forum, I suggest that you go back to the beginning, supply a brief timeline, an explanation of what you think is wrong, full line statistics, details of your wiring and filtering, details of your DSL router (model, version and, if you know it, firmware version) and details of what you've tried in terms of changing your hardware and cabling, as well as any steps you've taken to look for interference.
If you're not prepared to explain the problems you're having and are determined that Zen are in the wrong, I can't see what this forum or Zen can do to help now. I would suggest the best option for both you and Zen in this instance is for you to request your MAC code and find a new ISP. However, it's worth remembering that if you migrate to another BT Wholesale based ISP you will take any issue with you to your new ISP and if the issue is to do with pair quality, you will take the issue with you whichever ISP you move to.