The way I did it the day after BIS 2.0 was launched by cingular,
You have to talk to tech support chat
(support.cingular.com)
Ask them to delete your bis account including your username (so you can use it again), dont tell them you are going back to 1.8!
After that, register via this site on 1.8
https://webclient.blackberry.net/Web...ite=mycingular
This info is free of charge only today!