It is difficult if your phone is bugged with FlexiSpy. On Android phone, you can install Symantec Norton Mobile Security which claims to be able to remove the spyware.
There is another popular mobile spy software called SpyMobile.
They support virtually any mobile OS - iPhone, Blackberry, Android, Windows Mobile and Symbian - which means they can be installed on almost any device. If this application is installed on your mobile phone, it is running in silent mode so there is no way to know whether your phone is bugged.
If you want to know
Windows Mobile and Symbian: #123456789*
Symantec Norton Mobile Security:
Mobile spyware review:
More information on signs of bugged phone: