Help how to solve bad signal reception?


signal reception on my s4 is really bad in my locality but when i use the same sim on a simple nokia mobile the network bar is full. i have tried using signal boosters all it does is toggle the airplane mode. is there anyway i can improve it without having to using signal extenders etc. my s4 is rooted. i read somewhere about flashing a new modem and i have no idea about its workaround. any solution?:(:(:(