AT&T SIM Card Not working in Cingular Smartphone

I recently purchased a used, perfect condition Treo 600 that's branded as a Cingular device. Unfortunately, when I put in my AT&T SIM card (it's a prepaid SIM Card) the phone doesn't detect the network, even when I hold down the power / end button and search for the network.

Any suggestions?

---

› See More: AT&T SIM Card Not working in Cingular Smartphone

The reason why is it's not working is because if the it's just AT&T and not the New AT&T it won't work on a Cingular phone you would need the New AT&T Prepaid Sim Card (or Cingular), the Old AT&T sims card won't work on a Cingular phone. I hope this helps out for you.

Originally Posted by shantellylace7

The reason why is it's not working is because if the it's just AT&T and not the New AT&T it won't work on a Cingular phone you would need the New AT&T Prepaid Sim Card (or Cingular), the Old AT&T sims card won't work on a Cingular phone. I hope this helps out for you.

That is incorrect. The Cingular network and the new AT&T network are the same. The old AT&T Wireless Service network is different.

Originally Posted by NH2010

I recently purchased a used, perfect condition Treo 600 that's branded as a Cingular device. Unfortunately, when I put in my AT&T SIM card (it's a prepaid SIM Card) the phone doesn't detect the network, even when I hold down the power / end button and search for the network.

Any suggestions?

Look at the network settings to make sure that the phone is set to operate on 850/1900 MHz rather than 900/1800 MHz. Some older phones did not have automatic band selection.