You should take immediate precautions to disable your phone from being used. These will vary depending on the manufacturer and the OS of your mobile phone.
As soon as you have a replacement phone in hand, follow How do I access my Bitkey wallet using my new phone? for more information.
Note: If your phone was unlocked at the time it was lost / stolen, and you have set up Mobile Pay transactions, it’s possible that whoever is in possession of your phone can make Mobile Pay transactions until you initiate a recovery request, at which point Mobile Pay will be turned off.