Can I buy the iPhone 5s / iPhone 5c without a contract?
Yes, both the iPhone 5s and the iPhone 5c will be available on September 20 unlocked and without a contract from T-Mobile. Both phones are subject to off-contract pricing, which is significantly higher than subsidized prices offered to subscribers with a two-year service agreement.
Click here for more information on iPhone 5s prices, with and without a contract.
See this link for more information on iPhone 5c off-contract and subsidized pricing.