Help... Cloud Wifi does not remember my number

I got my 8gb iphone on UK release day and have registered for an O2 iphone contract. The problem I have is that every time I have to use the Cloud Wifi hotspots, it asks me to enter my number.

Isn't the cloud network supposed to remember my MAC address of the iphone and automatically log me on to the network. This is becoming a bit of a problem because quite often there is a Cloud network near where I am and I am waiting for an email to come through. But 10 minutes later I realise that I'm not receiving anything coz the phone has connected to the network, but its not authenticated and so no data transfer is happening. I manually enter the number again and suddenly I have 10 emails in my inbox. This happens again if i lock my iphone and leave it for about 15-20 minutes. It loses the authentication to the cloud network and no data transfer.

Anyone else have this problem?? Any solutions anyone?

As I travel quite frequently and use local sim cards wherever I go, I have unlocked with iPwner. I have tried restoring to stock apple 1.1.4 firmware, but still no luck.