T-Mobile USA today announced that its variant of the Samsung Galaxy S 4 will be available online beginning April 24 and in stores May 1. It will require a downpayment of $149.99 and 24 monthly payments of $20. T-Mobile is only selling the 16GB model, and has no plans to sell the 32GB or 64GB models. In related news, Sprint today announced its specific launch details of the Samsung Galaxy S 4. The GS4 will be available at Sprint stores beginning April 27 and will cost $249.99 with a new line of service or eligible upgrade. Sprint is offering a $100 discount on the GS4's price to new customers who switch their number from a different carrier, which drops the out-of-pocket cost to $149.99. Preorders for the Galaxy S 4 begin April 18. Sprint's Unlimited Everything plans start at $79.99 per month.