According to The Intercept , the NSA is secretly monitoring calls in Kenya, the Bahamas, Mexico and the Philippines under a program called MYSTIC. The NSA is using MYSTIC to gather personal data on mobile calls placed in countries with a combined population of more than 250 million people. This information was discovered from the cache of documents provided by NSA whistleblower Edward Snowden.
Definitions of terms related to the MYSTIC program, drawn from an NSA glossary
NSA scrapes Kenyan mobile networks for metadata which reveals the time, source, and destination of calls. The code name for the Kenyan component of the program is called “DUSKPALLET†and it seems that the metadata is saved with ‘the possibility for retrieval of content later’. This probably means that they can access more call content later if need be. It is unclear how the NSA gets the call data from Kenya but the operation is apparently sponsored by the CIA.