check out the sky forums first, used to be with Eclipse but escaped a while back
Phone up Eclipse customer service, ask for MAC, wait 5 business days, get mac in email. mail that to new isp
they give back money for credit, but their accounts are screwed and theywill try and take more money, they did so with mine or at least they would have done if I had not cancelled the DD.
I did however pay off the account fully and they confirmed that AND then tried to charge me for more