I have purchased T Mobile Prepaid sim card with a plan for 2 weeks for US$30.00, it was unlimited talk, message and data. A seller in Korea told me to put sim card upon arrival. I did exactly what I have been told but unfortunately, I didn’t have no service in US. I have contacted a seller in Korea to resolve the problem. Instead of resolving problem, this seller was telling that there is nothing he can do about it and trying to transfer responsibility to a US based T Mobile prepaid dealer who was supplying sim cards and plans to Korea. There are number of US local prepaid dealers who are selling T Mobile prepaid plans in Korea with some other nations in Asia(China) without consent from T Mobile company. I have found out this when I stopped by a local T Mobile Store to resolve an issue that it is not allowed to buy T Mobile Prepaids in another country other than US.
IF this is true, T Mobile has to control their US local dealers to prevent fraudulent activities to keep innocent people to get wrongfully doing business with these people.