main lcd display malfuntion on my cell phone

i have a couple of cell working phone units which have lcd issues. these units bears two lcds mainly the outer lcd which is the caller id found mostly on most flip phones like motorola v series units (e.g. v300, v400, v500, v600, samsung e715, samsung e105 etc. these units are in working condition and audio works fine. howver when you power it on, you do't see any displays on the main lcd but and everything else works. you can make and receive calls, keypads work fine etc. in a nutshell, imagine a blind person having to use a regular cell phone or using your unit with your eyes closed.