One cell phone is one jammer
With a cell phone, there is a "jammer" for the cellular signal. Let's recall what a "jammer" is: it is a noise generator at the frequency of a wanted signal. Is there a way to directly cancel out the interference? No, because you can't see the stars when the sun is there. The sun is too bright, and the stars are too dim compared to the sun. The principle is the same for radio signals: "jammers" make too much noise compared to the signal level of your cell phone.

However, a cell phone, or rather its radio modem, has one important characteristic. The farther the phone is from the base station, the weaker the signal from it, and the more powerful the transmitter is needed to ensure a reliable signal from the phone to the cell tower and from cell tower to cell phone. If the base station is far away, the phone can increase the signal strength, and vice versa, if the base station is nearby, reduce the signal strength.
What happens when there is a strong source of noise near the phone? The phone thinks the tower is far away and starts to increase the power of the transmitted signal to the maximum in order to eventually reach the tower and get a response from it. And this maximum transmit power is often enough to guarantee communication with the nearest base station, even in the case of a "jammer". The probability of this "fuzzy" registration in a cellular network is very high in cities, especially if the noise source is behind the phone relative to the tower.
Also, no "jammers" won't work forever. And GPS markers can work autonomously for up to three years on a single set of batteries.
jammer gps devices that generate noise at satellite navigation system frequencies. Their purpose is to prevent GPS/GLONASS receivers from receiving signals from satellites. Here, the task of the "jammer" is very simple, because. The signal level from the satellite is so low that wrapping the receiver in thick foil is enough to make it impossible to pick up the already weak signal from the satellite.
However, there is still a way to combat this jamming method called LBS. The system involves using the cellular operator's towers to determine the coordinates. By analyzing the signal strength of each base station that the GPS Marker "sees", and knowing their coordinates, a rough estimate of the coordinates is possible. The accuracy of this determination is not high, but it allows you to find the area and sometimes the building where the GPS marker is located. In most cases, this is enough to identify the search area, and will almost always allow you to find marked and stolen cars.