Use the phone's security features to protect yourself
Most phones have security features which you can use to stop other people using your phone.
For example you can set a Personal Identification Number (PIN) which must be entered before anyone can use the phone. Read your handset User Guide to find out what features your phone has and use them.
Even if your phone isn’t stolen this feature protects you from someone who might be tempted to ‘borrow’ your phone and make a few expensive calls without your knowledge.