T-Mobile customers with Wi-Fi calling capable handsets (all Android phones) can add Free Wi-Fi Calling to their rate plan at no additional charge. Calling via Wi-Fi doesn't use up your plan minutes and so can be a big money saver.
Finally I have a really good reason to ditch my home phone number!
T-Mobile is excited to expand our Wi-Fi Calling feature, a unique and valuable service T-Mobile has been offering customers for over three years. Starting today, T-Mobile customers can add Free Wi-Fi Calling to their rate plan – at no additional charge – to place calls over Wi-Fi without deducting from their allotment of minutes. This new feature is available at T-Mobile retail stores to all customers on Even More and Even More Plus Postpaid rate plans who have Wi-Fi Calling capable handsets.