Welcome to Vodafone Community
Very basic limited info such as a few contact mobile numbers can be saved on a sim card if a phone allows it @iismeme
Your not able to save anything else on it.
Move what you can to a Sd card but If your phone does not accept a sd card then I'd suggest to delete data such as...
Old contact numbers.
WhatsApp texts etc.
Clear apps caches.
As a last resort back up and factory reset.
🌈 Stay Safe 🌈
Current Phone > Samsung Note 10+ 5G _256Gb > Model: SM-N976B.
Samsung One Ui 2.1 / Android 10.
Samsung Gear s3 Frontier Watch.
Samsung Galaxy Buds.