The OBF policy is something you signed for and atleast an option you can use, especially if you upgrade to a S60 mobile, they always give you **** and 1 in 3 are faulty, If its a faulty phone which is not a surprise if you use nokia, at least you can change it for a new one, even if your phone software starts acting up after 6months, if vodacare sees it to be faulty they give you a brand new phone!!
But back to the mtn sim card issue, its fair I think that you should have your voda sim in the phone to claim from vodacom, it makes sense doesnt it?
Besides the insurance use the same policy, if your master line is insured to your N8800 and you start using an Mtn sim in the 8800 and your master voda sim in a K750 and 6 months should your 8800 get stolen you cant claim for the 8800!!!!