[AC Question]

Recently I had purchased Lenovo A7000 android mobile.when I selected the option preferred network I found that the option column is blank.when I inserted another SIM card I could find the option preferred network but after two days the same problem occurred. what is the solution for this?

[B. Diddy]

Welcome to Android Central! Do you mean the option to select 2G/3G/4G? Or the option to select the preferred network operator?

You ultimately might have to try a factory reset. There are other things that could be considered, but it doesn't look like that phone allows the user to wipe the system cache partition, and reinstalling the firmware would require you to root it.