Android
View Messages Saved on SIM Card auf Android
Modern Android phones save text messages to internal storage by default, but older SMS or messages received during a carrier switch can still sit on the SIM card itself. Google Messages does not show these automatically because it treats phone storage and SIM storage as separate message pools.
To find them, open the app and go to Tap on Messages ➔ Tap on Google Account ➔ Tap on Messages settings. From there, select Choose a SIM card (Dual SIM) if your device has two SIM slots, then tap Tap on SIM card messages to load the stored texts.
Why this happens
Carriers and older devices used SIM storage as the default location for SMS before app-based storage became standard. When you insert an older SIM into a new phone, those legacy messages remain on the card until you view them through this settings path.
When to use a different fix
If your missing messages arrived after switching phones and were never on the old SIM, checking SIM storage will not help. In that case, check whether Messages backup and sync is enabled, or contact your carrier if messages disappeared during a number transfer.