When the US's fourth-largest carrier T-Mobile finally introduced the iPhone 5, the company said it would only charge $99 (£65) down when on T-Mobile's 24-month "UnCarrier" payment plan. But things have changed. Now the carrier says the $99 was introductory pricing and has bumped the minimum down payment to $149.

Essentially, if you want the 16GB iPhone 5 on T-Mobile you'll be paying $20 over 24 months on top of the $150, which still makes T-Mobile's offering the cheapest out there. However, many are baffled over the pricing change, as it wasn't very clear the $99 would last for less than a month. 

As we explained in March, the UnCarrier plan allows customers not to sign a two-year contract but instead pay full price for the iPhone 5 at time of purchase or make payments for the next 24 months. Once the payment period is up, the phone is unlocked and yours to take to any carrier. The price for the 16GB iPhone 5 at T-Mobile has increased from $579 to $629 -$20 over the retail price at Apple.

The news of the pricing change was first reported by TmoNews, which got a look at promotional material within the carrier. The $50 increase also applies to the 32GB and 64GB models, requiring a $249 and $349 down payment respectively. 

Last week, T-Mobile announced its first set of financial earnings since finally making the iPhone available on its network last month. The company said it had moved 500,000 iPhones in total since its being available on its network on 12 April - which, when you think about it, isn't too shabby considering the iPhone 5 has been available for quite some time.