T-Mobile is now offering $1 per day calling with free T-Mo to T-Mo calls and unlimited 7pm-6:59am calls. The details:
Pay By The Day gives customers the wireless value they want without long-term commitments. The new prepaid plan only costs $1 per day for the days the phone is used. In exchange, customers get free T-Mobile to T-Mobile calling all day and unlimited nationwide calling from 7 p.m. to 6:59 a.m. All other domestic calls are just 10¢ per minute and text messages are 10¢ to send and 5¢ to receive.
Pay By The Day joins a growing family of prepaid options from T-Mobile, including Pay As You Go (previously named T-Mobile To Go) and Sidekick Prepaid (previously named Sidekick To Go). With no annual contract, no credit check, and no monthly bill, prepaid plans are a simple, direct way to go mobile.
I bought a prepaid phone from TMobile and I am very disappointed by the service!!! I bought the plan, and then called to another US number that provides international calling services. I called the number then connected to another number in Europe. Basically T mobile should charge me only for connecting to that US number and another company has to charge me for the international call. However, somehow T mobile charges me for international calls although they did not provide that service. Customer service just told me in their system my call appears as international. This is a stupid situation. Imagine you buy a prepaid international calling card from Wal-Mart and then call to toll free number to make international call. T mobile charges for calling the toll free number and also charges the international call according to their rates, although they did not provide that service to me. Customer service told me that they do not support prepaid cards and it is written in the contract conditions. I could not find anything about it in the contract. In any case, TMobile does not have right to charge me for the service that you did not provide!!!
So, why are you using a cell to call 800 to call international. Just get skype, duh, it is like $5 a month for 10,000 minutes. Seems strange what you are trying to do.