In this letter, a reconfigurable single elemental Substrate Integrated Waveguide (SIW) antenna is developed aimed at operating at 28 GHz as well as 38 GHz. The two PIN diodes used as switching elements shift the antenna resonance between 28 and 38 GHz when one of them is switched off. Also, dual bands are realized when both switches are made off. The developed antenna provides sufficient gain and enhanced efficiency to meet the requirements of 5G. This is accomplished by structural modifications of the SIW structure by stretching the flaring part of the tapered section introduced in the antenna. The tapered section provides good impedance matching. This reconfigurable SIW antenna uses Roger 5880 substrate and input coupling of K type connector. When S1 is turned off and S2 is turned on, the antenna responds at 38 GHz with a surge of 9.42 dBi along with 97.49 percent efficiency. As S1 is turned on and S2 is turned off, the antenna responds at 28 GHz with an increase of 7.33 dBi together with an efficiency of 98.54 percent. The antenna has a dual band response at 28 GHz along with 38 GHz with a gain of 7.23 dBi together with 9.6 dBi, and efficiency percentage of 99.14 percent and 96.96 percent when all PIN diodes are turned off. The simulations were performed using CST Studio Suite along with the computed outcomes are established in a better agreement with the simulation results.