Typically the electrical or telecommunication systems are not to blame as the source of the electrostatic voltages which result in the painful shocks. Sometimes the source may be atmospheric in nature. However, this is a more rare phenomenon if the system has proper surge protection. In this article I am addressing only the shocks caused by electrostatic charges accumulated on the personnel and discharged to other persons, the equipment or through the headsets. In other words, the personnel themselves charge up their bodies because they wear clothes and shoes, which generate electrostatic charges when they scoot in and stand up from their chairs and when they walk on the floors.
Most headsets have some sort of insulative piece that cushions the ear to the headset speaker.
The distance of this will hold off and arc of approximately 20,000 to 35,000 volts on the person. This means that by the time the electrostatic potential is great enough to jump, it is sufficient to cause physical pain. Most call centers have normal office style chairs, which have no antistatic capabilities. Also most call centers have normal carpeted floors with carpet that has little ability to keep static charges down against many shoe types. This does not guarantee that the voltages on a person at any other humidity or wearing any other shoe will be less than 3,000 volts.