SIM card from Motorola V400 won't work in Motorola RAZR V3xx

Just upgraded through Cingular online to a V3xx from V400. Didn't want to activate new SIM right away since I only use phone for calls. I put V400 SIM in V3 and it won't function. None of the keys work and eventually it shuts itself off. When I put the unregistered SIM in the V3xx everything works again, except calls. And when I put the V400 SIM back in the V400, everything works including calls. I thought all SIMS were interchangeable and now I am worried that the V3 SIM won't work in my V400 when it is activated. The V400 is quad band and came from Cingular unlocked, so I use it when I travel.

I had also planned on saving my phone book to the V400 SIM and then putting it in V3xx to copy, but that won't work either. Is the problem that the V3xx needs a 64K 3G SIM and the V400 has a plain 32K? Any help would be appreciated.

I believe you've answered your own question regarding the size difference of the SIMs. However, and I did this, you should be able to put the 64K in your V400 and copy the phonebook onto it. I would imagine that you need to register is first.

Geri O

the v3xx is a 3g phone that does require a 3g sim card. with out it your phone won't function. the v400 will accept the 3g sim card if and whenever you need to switch it back

Actually, you can use 64k in 3g phones and vice versa.

Thanks for the replies. I quickly discovered that the 3g sim is backward compatible, but the 32k sim is not forward compatible. This works out well since my V400 is still usable for travel and the V3xx RF is so good I no longer need a Wilson antenna to make calls from home.

Yep, you need a 64k to operate a 3g phone.

SIM card from Motorola V400 won't work in Motorola RAZR V3xx

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