The phones were obtained via a contract signed on July 13, 2015 with a company in Ethiopia identified only as "Miscellaneous foreign awardees", the typical identifier for many overseas contracts with the US government. The contract was handled by the State Department through the US embassy in Addis Ababa, the capital of Ethiopia. A compilation of screenshots from the contract is shown here:
It remains unclear exactly who used the cell phones during the Ethiopia visit, or what happened to the phones when the visit was over. After an initial response from the press office of the State Department about the contract, a state department spokesperson subsequently deferred to the White House, saying, "After speaking with my colleagues we think you should contact the WH Press Office for any comment on the President’s trip to Ethiopia."
The White House press office did not respond to a request for an explanation of the cell phone contract.
Note: A version of this post first appeared at The Weekly Standard.