Archiving text messages

Hi,
I can see my existing individual messages (brought in on my SIM card from my retiring phone), but when I want to view all text messages (messages | "all messages") I get a warning "SIM card full. The SIM card is full. You must remove some messages from your SIM card to receive incoming messages."

I want to keep my messages. The user manual says to tap "Copy to phone" (p.103), but the menu only shows the options "new", "reply" and "delete". And the former two give the same warning.

Is there a way to archive my messages?
TIA
Steven