How to cut your SIM card (Micro SIM, Nano SIM - iPhone 5) - YouTube
The above is a youtube video that shows how you can do itself. If you don't feel comfortable doing it yourself (I gather it's pretty easy) - I'm sure if you go to the type of shop that does cell phone repairs or does unlocking.- They should do it without much of a charge. Carrier stores in the U.S. often do that for their own customers.
Of course my reply assumes you can easily get a "regular" SIM.
Make use of T-M's UMA/wifi free calling from any place in the world with access to wifi. I use an LG G6, wife an S7)
A/o Oct 20, 2013 no need for intl prepaid as T-Mobile U.S. includes voice roaming at 20¢/min (in and out)., unlimited text (in and out), and unlimited data in 140+ countries.
My Plan -[6 lines] U.S. T-Mobile unlimited minutes (incoming and outgoing), unlimited text, fast data on each line. that $145/mo. total! . (In U.S. no surcharge for calling a cell.) If a line exceeds 2G of data in a month, pay $10 more for that line. [That only happens a couple times/year.