Contact your network to block the phone and the sim card to stop any unauthorised usage.
As mentioned previously change any sensitive passwords.
Try using the Find my phone option and or give it a ring as someone may be looking after it until someone calls , or it maybe in your home ,or check your social media such as Facebook to see if anyone has made a post. Do this before you have the phone and sim blocked.
If the phone cannot be recovered then make a claim against any relevant insurance policy using a police crime number.
If I can be of any further help then please don't hesitate to ask. 😎
