Mobile phone error message

[MalcolmY]

I have just turned on my Nokia 6100 mobile and have got the error message 'Insert SIM card'. I've tried taking it out, and putting it back again, but the phone just refuses to accept that the sim is in. Strangely, when I put this same SIM card in my spare mobile it works fine and, similarly, if I just swap over the two sim cards both work fine in the 'wrong' phones.
Phone A + Sim card A ----- doesn't work
Phone B + Sim card B ----- works OK
Phone A + Sim card B ----- works OK
Phone B + Sim card A ----- works OK

Both phones are fully charged.

I would prefer to have my original (Phone A) working normally as my spare is a PAYG and is the size of a small shoe box. Any ideas please?

[chelle7272]

Are both sims the same network and are both phones able to accept any network?

[MalcolmY]

Both are Vodafone.

The problem phone has worked OK for 5 or six years and not given a scrap of trouble until today. And no, I haven't dropped it or abused it in any way.

[Prudie]

Try taking the battery out for a few minutes and then re-assemble. Anything's worth a shot