In Blackhat (2015) at about 32 minutes into the movie, Mr. Jessup tries to call Mrs. Barret but is unable to call her. He uses an Android phone. The hacker offers help and he enables roaming and then changes the refresh rate from 1 hour to 1 day and then hands back the mobile. After that Mr. Jessup is able to make the call. What did the hacker do to fix the issue?
First of all I would like to point out that they are citizens of US and investigating a cyber security issue in foreign country.
Mr. Jessup is not a tech savvy guy and had kept the roaming off while in US and forgot to turn it on once they touch down on foreign soil.
Hathaway(hacker) just turns on the roaming to enable calling since they are outside of US. Spotting this as opportunity he browses the app handling his GPS monitor and switches it's refresh rate from 1 minute to 1 day which will update his location once in a day in case he needs to escape.
Which officials recognize at 01:23:00 and switches refresh rate back to 1 minute.
So, switching refresh rate had nothing to do with calling issue. It was only roaming switch which needed to be turned on.
The scene of the phone problem is Los Angeles, NOT in foreign soil. So the roaming idea is not very valid. Maybe the agent did not turn on the Roaming to be available in other US city different from his city of origin, but even in 2015 the roaming services were automatic within the continental US.