T-Mobile has seen better days. First, it looks as though T-Mobile will be acquired soon by AT&T and to pour salt in their wounds apparently the subscriber results for Q1 2011 have been atrocious. However, T-Mobile is still doing all it can to win back its customers by revamping its prepaid plans to allow for unlimited data, launching cutting edge handsets, and now allowing unlimited calling over wireless networks.
TmoNews has gotten hold of a screenshot that shows that calls over wireless networks will be completely free from tomorrow (May 11th).
Right now you can make calls over a wireless network, which is useful where your data coverage is poor, but on the flipside, it cuts into your in-plan minutes. Logically this always seemed unfair, since the wireless network you are on is ostensibly not connected with T-Mobile in any way. In fact, it is likely that you are paying twice for this "service," once for your wireless network and once for your T-Mobile in-plan minutes.
T-Mobile has rectified this seemingly unfair situation by allowing users on the Even More, Even More Plus, and 4G Do More plans with "capable phones" to make unlimited calls for free wherever they are connected to a wireless network.
In the next few days, customers with capable devices and on the appropriate plans will receive an SMS directing them to T-Mobile.com to add the feature.