Hi Gaothar,
I've checked my eir a/c to see if there is any additional link to something for cancelling account - under "support" link for phone, I'm getting "503 - Service Unavailable", also, no online chat services, but I found this in the community:
[broken link removed]
but you've gone through that already with all those "lovely" phone options.
Re the "online form", can you try a different browser - that confirmation for being a human might be tied to your browser settings - try IE / FF / Chrome - see if that works for you.
Failing those, you could try posting on the community, or trying twitter / Facebook to interact with the Eir support team.