[ks2014]

I just receieved a white Z10 (STL 100-4). It is a Verizon branded phone but purchased it online as an unlocked device. I put the ATT GoPhone SIM into it from my ****ty ZTE phone and all it does on the Z10 is display either a lowercase or uppercase 'E'.

[raino]

Yeah, that's all you're going to get--2G (EDGE.) This is a Verizon phone, it wasn't designed to work on other US networks all that well. Hell, it isn't even as compatible with Verizon as other BB10 phones are.

[scrannel]

As raino says... Verizon phones are designed for their CDMA network. The unlocked, GSM side, is for overseas use, so it's called a dual mode phone. But US GSM frequencies barely support it.

[lift]

I just receieved a white Z10 (STL 100-4). It is a Verizon branded phone but purchased it online as an unlocked device. I put the ATT GoPhone SIM into it from my ****ty ZTE phone and all it does on the Z10 is display either a lowercase or uppercase 'E'.

There are so many sellers online (ebay, Amazon) that are VERY misleading selling the Verizon Z10 as an "Unlocked" Z10. It really gets me mad as to how many are doing this. They know the phones are unlocked for use overseas on GSM only yet they still sell them as "unlocked". If I were you, wherever you bought it from, I would file a complaint against the seller for being deceptive and demand a full refund.
If you are looking for a Z10 for GoPhone you need the STL100-3. No other version of the Z10 will work properly.

[raino]

The unlocked, GSM side, is for overseas use, so it's called a dual mode phone. But US GSM frequencies barely support it.

BB corrected it somewhat with later phones (Q10 onwards,) but the Verizon Z10 is especially bad. The Q10 and Z30 both would have gotten the OP at least 3G/HSPA+ on AT&T, maybe even LTE if he were in a band 4 market (not to mention...band 4 LTE on Verizon.) Same with the Verizon Classic and it's more of a "world phone" than any previous Verizon BB10 phone.