Ok. Well apart from complaining on here have you done anything about it? Rung them and asked for your box to be checked or your signals checked? To be fair if they don't know you've got a problem they can't fix it.
Firstly I'd like to welcome you to the forums and say that I'm really sorry to hear that you're still experiencing this issue with the error message.
I've taken a look at things from this end, and can see no major issues, however when I look at the account I can see that the last time you contacted us regarding this fault, our second line team did some additional checks and made some changes. Their notes state that if this continues to happen then the next step would be to arrange for someone to call out and investigate further for you.
So I think it may be best to arrange this. I've sent you a private message in order to get things moving. Please look to the top right of this page where you'll see a purple envelope icon, click on this and you'll see my message.