Looking at the comprehensive chart I created last month:
Cingular charges - 1.99/min.
T-Mobile charges - 4.99!
You would have to make sure intl. roaming is acttivated. A Sprint or Verizon phone won't work. Equador uses the 850 band - same as Cingular here. Most, but not all, Cingular and T-M phones work on 850 as well as 1900. You would need to get the unlock code from your carrier if you are going to use another SIM. That would be the way to go.
Is there cell service where she will be? Go to
http://www.gsmworld.com/roaming/gsminfo/cou_ec.shtml
and click on coverage map to get a vague idea ov coverage
Neither United Mobile or TravelISM work there. CelTrek does at $1.39 for incoming and $1.49 for calling the U.S. With CelTrek you get a U.S. number.
Since she'll be there a while, it may pay to get an Ecuadorian prepaid SIM to stick in her phone. Don't know cost.
...mike
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.