T-Mobile USA announced yesterday that the iPhone5 will be available in its stores from 12 April, followed by the Samsung Galaxy S4 on 1 May.

The two popular smartphones fill gaping holes in T-Mobile USA’s device portfolio. What’s more, the HTC One is expected shortly. The BlackBerry Z10 is already available from T-Mobile.

Each of these devices will be able to access the operator’s nationwide HSPA+ network and its newly-launched LTE network in seven metropolitan areas.

The new devices are part of a wider plan by John Legere, chief executive, to shake up the US wireless industry and help the country’s smallest nationwide wireless player claw back market share.

Speaking at a New York press event this week, Legere confirmed that T-Mobile had scrapped annual network contracts.

By separating tariff plans from device costs, Legere says customers are given much more flexibility as they are not forced into packages that carriers dictate for particular models.

Moreover, in a bid to undercut rivals, T-Mobile will charge a $99.99 upfront fee for its high-end devices followed by 24 monthly payments of $20. By contrast, AT&T, Sprint and Verizon Wireless require a $199.99 down payment for their top-of-the-range devices.

The older versions of the iPhone – the iPhone 4S and iPhone 4 – have down payments of $69.99 and $14.99 respectively. The iPhone 4S has 24 monthly payments of $20, while iPhone 4 customers pay $15 each month for two years.

Legere says an iPhone 5 and monthly data plan bought from T-Mobile would be $1,000 cheaper – over a 24-month period – than an iPhone from AT&T on a comparable data package. And unlike the iPhone 5 on other networks, added the chief executive, T-Mobile’s will have HD voice.

If a T-Mobile customer wanted to leave the T-Mobile USA network, outstanding payments on the device would have to be paid before it was unlocked. Alternatively, the device could be traded in – at “fair market value” – at a T-Mobile store.

For qualified customers with a sound credit history, T-Mobile’s monthly network rates can be settled on a post-paid basis. There is also a pre-paid option.