T-Mobile now has the Lumia 640 available on the US carrier's website, ready to start shipping. As previously covered, this Windows Phone will be available on 'Ship to (direct fulfillment)' system, meaning you'll need to order the handset online or through telesales. The product will then be shipped to a supplied address or local T-Mobile store.
If you're interested in the Lumia 640, the Windows Phone will set you back by $55 per month on a 24-month plan (cost of phone and plan together). This option will bag you the Lumia 640 directly with $0 down. Full retail price through T-Mobile is $129.84, which will need to be settled should you cancel the service prior to the contract coming to a close.
T-Mobile is also offering free overnight shipping in time for Father's Day, ending June 17. If you'd rather not order directly through T-Mobile, Walmart is set to stock the Lumia 640 too.
Source: T-Mobile; thanks, Jon M., for the heads up!