Getting no-Plaze fast with SMS!

When I try to enter my mobile number in my profile to use PlazeSMS, I get a message saying that number is already registered.
I've never registered for Plazes before this week. I am, of course, the only one with that mobile number.
Your e-mail support told me I'd probably registered before, with another email address (I haven't) or directly with my mobile (how would I have done that?) creating the account associated to the mobile number (whatever that account is).
So... I've tried requesting passwords from all the email accounts I might have registered with - and there is only one.
I've gone to Plazes.com with my mobile to see if there was anyway to login there differently, but no go.

What now are my options?
I am unable to associate my mobile phone with the Plazes service - which renders this service almost useless as I am in the mobile industry (hint...we'll be on the same team soon)

best,
-C