When Can I Upgrade My Contact?

I'm currently on a 24 month contract with T-Mobile, but as my iPhone 4 is starting to die of a slow death I would like to upgrade as soon as possible.

At the moment I have been on this contract for 15-16 months. Does anyone know how soon I can upgrade? I've heard mixed reviews of people getting upgrades between 3-6 months before their contract was due to end?

Tmobile allow upgrades in the final month of contract.

If they allow an earlier upgrade, you will be tied in for an additional 8-9 months, or face paying upfront for the final months of the existing contract before signing up for a new one.

Call customer services and ask.