I am confused! I have transferred SIM cards (Orange) from one phone to another before, and both the Phone Numbers and SMS messages have moved to the new phone.

I did this again the other day, but this time the Phone Numbers moved but all the messages vanished!

I then put the SIM card back in the original phone and again the Phone Numbers showed up, but no text messages.

Can anybody explain this please.

Many phones store Contacts AND/OR Messages on the phone itself.

The SIM card is more limited in what it can store, so phones store the contacts in their own memory (so that things like pictures and detailed information can be included). They also offer more room for messages.

In this case, your phone probably stored messages on its own memory and for whatever reason, changing the SIM card erased them.

What phone models were you using?

The original phone is a Motorola V545 and the new one is a Samsung J700.

most modern phones barely touch the sim card for storage of these things.