"We interceded to get him out of the general prison population," Nelson said. This served to remove Hammar from contact with dangerous inmates.
The calls have since stopped, his mother said.
"He is now being kept in a low ... intensity place, more like an administrative place," Nelson said.
But because of the low security of the new facility, which Olivia Hammar describes as a storage shed, officials periodically chain Hammar to his bed.
The Hammars recently turned to their U.S. congresswoman, Ileana Ros-Lehtinen, who heads the Committee on Foreign Affairs.
"This is outrageous," Ros-Lehtinen said. She has spoken with the State Department and the U.S. ambassador to Mexico, and will meet with the Mexican ambassador to the United States this week. "Enough is enough," she said.
"Jonny, we're going to get you out of there," Olivia Hammar said to her son by phone Friday.
He reminded her that she has been telling him that since August.
Their son returned to them safe and unharmed from Iraq and Afghanistan. Hammar's parents now fear they could lose him just across the border, if they wait too much longer.