Do you still have text messages in your mobile phone?

It's still there. It affects the operating system and has little to do with your information and phone book, but some of it will be erased. I suggest you back up your information and phone book.

Sim card can store short messages and phone books, but its capacity is relatively small.

If it is a Nokia machine, back it up with a PC suite.

If not, you can only find more important information and phone numbers to copy into the SIM card.