Samsung S3 Issue

So I have had this phone for some time now I like it, however, recently sometimes when I try to make a phone call it immediately drops the call when I hit the call button.  There are other times when I try to make a call and all is fine.  I did read somewhere that if you go into airplane mode and out of airplane mode it will work, which it does each and everytime, but I am getting tired of doing that now for the last 2 months.  If anyone know how to fix this I would greatly appreciate it.  I have tried to search the net but have not found anything.

if u have everything saved up on the external hd and all your contact info link to google then i would suggest doing a factory reset. but before you do the factory reset i also suggest you do a backup first just in case you forgot to save something and can revert back and retrieve.