Quick check/scan if any of your installed applications could send/write sms/mms/wap messages.
Some malicious apps may cost you money by sending messages without your confirmation. This may result in unexpected charges.
Light, quick and no-ads.
Launch also the hidden "App Ops Settings" permission screen in android 4.3 & 4.4/4.4.1 KitKat to manage individual permissions for your applications.