There's a new free refill promotion going on right now at T-Mobile.com right now. Purchase
Eligible phones include the $74.99 Samsung :) t359 QWERTY slider
This is a great deal if you are thinking of upgrading your T-Mobile phone or switching to T-Mobile to take advantage of the operator's awesome $30/month unlimited data, texts and 100 minutes plan that's launching Oct. 16th. You need to act quickly though as this is a "limited-time offer". There is no stated expiration date but T-Mobile's free refill deals typically only last 2 to 4 days.
Update: it turns out that the deal does not apply not the Nokia X2 for some reason. That seems like a strange exclusion as it does apply to all the other over $50 phones on the T-Mobile site and that T-Mobile often sells the Nokia for less than the current $74.99 price.
6-Oct-2011: The free refill deal has ended