It’s great to be able to call anyone at anytime. But unfortunately not every phone user knows when to stop talking. In few places like mosques, library, meeting rooms, hospitals, movie theatres there are restrictions over using phones where most of the people don’t care to break the rule. There arises the need of a cell phone jammer. Cell phone jammer is an instrument which prevents cellular phones from receiving and transmitting the mobile signals to the base station. Cell phones are basically handheld two-way radios. And like any radio, the signal can be disrupted, or jammed using a cell phone jammer. We contemplate to present the design, implementation, and testing of a dual-band cell phone jammer which is cheap compared to the ones available in the market and very easy to carry. This jammer is targeted to work at GSM 900 and GSM 1800 simultaneously, resulting in jamming the well used mobile carriers of Bangladesh within a few meters of the device. The system works by generating a noise at the GSM frequency band, with a bandwidth wide enough to block the connection of the cell phone from the base station by generating an interfering noise that cancels out the base station signals immediately.For building up the circuit, we needed 555 timer IC, Capacitors, Resistors, Inductors, Variable capacitor (tuning capacitor), a transistor and a 9v battery. Initially we used the transistor MRF 947T1 IC but for not getting desired output power we used BFR96 as an alternate IC. Initially we implemented the design on a bread board and was able to block signals momentarily. Then, due to the movement of the wires and other components, we thought veroboard would be a good solution. But after implementing on veroboard the device didn’t work. We figured that due to our lack of experience in soldering, something had gone wrong and due to soldering the total resistance of the circuit has increased. So we implemented the circuit on breadboard again. Only if we had knowledge of designing and printing, printed circuit board (PCB) then we would have definitely gone for a PCB design. After a lot of adjustments and tuning the circuit gives out a high frequency signal as expected, but it’s not able to jam the signal all the time. Twice we succeeded to block 3 mobile phone operators of Bangladesh. They are- Grameenphone, Robi and Airtel. And several times we were able to drop the network bars from 4 bars to 1 bar.