The LG K4 Android smartphone was released by LG Electronics in February 2016. The LG K4 was the third smartphone released in LG's K series. The LG K4 covers various versions, including the K120E (Europe, Single-SIM), K130E (Russia, Dual-SIM), and K121 (Canada, Single-SIM).
It can be a problem with your service try getting a new sim card or speaking to you service provider. If its a problem with the software of the phone then resetting it should fix it.