You should contact your mobile phone provider to have your phone blocked immediately.
No account information is stored on the phone and access is protected by your username and password, mPIN or biometric information so your account shouldn't be at an immediate risk, but you should still have the phone blocked if you use contactless payments on services such as Google Pay or Apple Pay.
If you are using the same number, you just need to download the app again and log in. If you get a new number, you need to update your contact details with Suits Me over the phone or through the Suits Me online portal.
How do I update my contact details and personal information?