Your contacts, messages, apps, wallpaper and pretty much anything else that isn't your phone number will stay on your phone – even if you take the SIM card out. No need to worry about losing your email settings or your entire contact list (we get it, nobody knows anyone's phone number anymore).

No, you generally will not lose the text messages stored on your phone's internal memory when you change a SIM card. Modern smartphones (iPhone and Android) store SMS and RCS messages in the device's local database or back them up to the cloud (iCloud or Google Drive) rather than on the SIM card itself. When you insert a new SIM, the messaging app will simply continue to display your existing conversations. However, if you have very old messages that were manually saved to the SIM card (a feature mostly obsolete in 2026), you might need to "import" them to your phone's memory. The primary risk when changing SIMs is not losing existing messages, but missing new messages sent to your old number while the card is inactive. If you are switching numbers permanently, ensure you have set up your cloud backups (iCloud/Google Messages) and updated your account settings for two-factor authentication (2FA) and messaging apps like WhatsApp, which are tied to your phone number rather than the physical SIM.