Turn off (or stop) the function sim update on 7610 (or 6600)

I want to use a 3G simcard from the 3G-operator Three in my 7610. When I start it up it connects to Vodafone to roam and then it loses reception for a second and I get the message "sim update". After that i get the reception again and everything seems to be working ok until I move to another area and it connects to another base. Then I get the message "Sim not allowed". I�ve heard that the Three 3G-card would work if you can stop the sim update-function. Anyone who can help me with this?