You will be able to connect your iPhone to Telecom's new W850 network in June, until that time you won't be able to.
Telecom will have prepaid options on the new network, but as to pricing you, like the rest of us will just have to wait and see.
Warranty on your iPhone will lie with Vodafone. When you bring your own phone to any network, it is a best effort service (i.e. connection only).
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