A study by the Silicon Valley Business Journal found about one in four AT&T iPhone users would switch to Verizon if they had the chance.
However, most said they would wait until their AT&T contract expired.
Researchers say only 3 percent would break their contract, a move that can cost as much as $300 in "early termination" fees.
AT&T is currently the only U.S. cell phone service provider for the iPhone, but Apple and Verizon have been discussing a partnership for more than a year.
