I had them delete my portfolio in January and they did it within 48 hours. I was extremely polite in the email and said it wasn't anything against Crestock, I had just decided exclusivity at IS was the best for me.
Didn't have a problem. Sorry to hear your having a problem.
EDIT: I went and made sure that they were still infact deleted, and I can't even log into my account so I assume they are. It says:
"Sorry, this account has been deactivated.
Please contact
[email protected] for
further info and support."
when I try to log in.