Nokia 6300 on T mobile

Question

I have just unlocked a nokia 6300 on T mobile. I have inserted a vodafone sim which is on contract but when i try to get on the internet it will not let me. Everything on the phone is still geared up for T mobile but the vodafone sim works ok. I get a message saying subscribe to packet data, when i try to enter settings the default is T mobile and there appears to be no way to change it. Anyone have any ideas?