What either company won’t admit, is that T-Mobile doesn’t have a built in infrastructure, so they obviously had to lease for these facilities. After Cingular bought AT&T’s network, they leased it out to T-Mobile. Also included in the deal is for them to use Cingular facilities where the AT&T network is weak or non-existent. At times, when you’re not getting a good signal, the network will normally switch you seemlessly from either or network, which most users will never notice. At times, you’ll actually see the carrier name show up on your phone.

On most occassions, it normally will show if a T-Mobile customer jumps on the Cingular network, but not vise vesa. I’ve asked one of my buddies, who was an old SBC/Cingular tech (now AT&T), why and he states, it’s about the network coverage. There is simply more Cingular coverage than T-Mobiles (AT&T’s old network). Also, most T-Mobile phones are not locked. Meaning, the phone will not inherently find just one network and not drop, if no network can be found. For instance, you can put the SIM card from a Cingular phone into a T-Mobile phone and it will work. On most phones, if you do the opposite, T-Mobile SIM to a Cingular phone, it won’t work, because the phone is locked to Cingular’s network. For the most part, this isn’t the case with a lot of new phones, but some phones are still locked this way