If you are on T-Mobile you will be glad to hear this; if not, this might be one more reason to consider the carrier if you need the offer. “Unlimited calling to any domestic mobile number, including Puerto Rico, regardless of carrier” should be an offer going live on April 4.
Unlimited Any Mobile will be available, according to the image leaked above, as “a $10 per month subscriber-level feature”. If you already have a contract but need more minutes you will be able to add this to your account, without it being a contract extension. Another great feature is that the Unlimited Any Mobile feature will not change you current plan; you can choose to add it for a couple of months and then have it removed.