Unlocked phones on Carrier's

[Gubber22]

I read a thread some time ago that Verizion was going to start letting unbranded phones be used on thier network as long as its meets thier criteria. I called Verizon tech line, and was told they was not aware of this.
My question is : What network in the US if any allows you to pick your own phone to put it on thier network?
Their are a lot of other Windows mobile phones out their that are better then then carrier's carry, Ones that have more memory, display ect.
I am looking at the Sony X1 to purchase and thier are some others even better. I am still running the xv6800 which has poor memory. I have went into Verizon several times and looked at the Pro, but while testing it in the store I was not impressed with the Running memory when looking at it in the store. I am sure it does better then the 6800 but not enough for me to change, I have walked out the store twice. The Pro 2 really seems to be able to do what I would want on memory, but it hasn't even came out yet and Verizon I am sure will not put it in their line up till it has been out a while. So what network allows other phones on their network? I see all these unlocked phones you can buy but what good are they in the US?

[aarondeep]

Verizon really does not let you add another device to their network unless it was originally made for Verizon....

To understand unlocked phones and what not,

A locked phone means that the device will only work on a specific carriers network.
Once a phone is unlocked it will work on any carriers network provided that they are using the same protocols.
The 2 protocols used in the US:
GSM = ATT, T-mobile, others
CDMA = Verizon, Sprint, Alltell, MetroPCS, Cricket, others

Most parts of the world are GSM. Those phones you see online that come from other parts of the world are most likely GSM phones.

The problem with buying unlocked GSM phones is that other parts of the world use different frequencies for voice and data.

Read this article http://en.wikipedia.org/wiki/GSM_frequency_ranges

[Gubber22]

Thanks for the reply and in detail. This answers my question. I also have been replying on some of these other phones, and as I underdstand it, these unlocked phones will work adding the carriers sim's card ATT, T mobile and others But not CMDA
Thanks again