>>748660 from the matrix wiki:

Anderson is suddenly contacted by Morpheus via a cell phone mailed to his office, but is almost immediately captured by the virtual reality's Agents, led by Agent Smith. After refusing to co-operate with the agents, Neo has an electronic bug implanted within his Matrix-simulated body so that his actions can be tracked and those seeking to make contact from the free world can be traced and destroyed. He is then contacted by Trinity,[7] freed from the bug, and taken to meet Morpheus.