AT&T and T-Mobile are related in many ways.

They both use a technology called GSM. This means Global System for Mobile. They are carriers that are great for people who enjoy traveling internationally or if you travel internationally for business. GSM uses SIM cards which makes switching your phone easy...sometimes it becomes difficult, but it is somewhat easier. The issue is, the SIM Card fries very easily. Enter the password wrong a couple times...go by SIM Card.

The only differences between AT&T and T-Mobile is that AT&T is a larger network with more customers. They also offer different phones. T-Mobile is a smaller network and offer different phones. T-Mobile within the United States relies heavily on AT&T to provide a lot of their network coverage. They use more off network than on network. Also, T-Mobile has the smallest 3G network in the United States based on large carriers. AT&T isn't much ahead...they are the second smallest.

Within the United States, GSM is a minority...it is only primarily used on two large U.S. carriers: AT&T and T-Mobile. They lack a lot of coverage due to their limited roaming/network sharing abilities here. They also provide echoed phone calls. Calls also take longer to connect.

The only differences between the phones/devices with the two carriers is actually the device itself. They are pretty much identical as far as the internal workings go.

Originally Posted by onthesource

Could you tell us the differences between the two phone in the two networks? Thanks!

Good question.. they are both GSM carriers.. Pretty much the equipment slightly varies (T-Mobile has the Sidekick, whereas AT&T doesn't).

Could you tell us the differences between the two phone in the two networks? Thanks!