Be aware of excessive applications running in the background as well as screen brightness. If these simple fixes don't improve the battery life, the battery could be damaged which in case you would contact the manufacturer.
First, make sure that the proper antennnas are enabled (cellular data/ wifi are separate) this can be found in the network settings. Next, check that you are in a service area. The phone's signal meter in the top bar will signify signal strength or no service.