As anyone whose jumped from AT&T to Verizon (or vice versa) already knows, GSM and CDMA handsets aren’t compatible with each other. Everything we’ve heard about LTE seemed to indicate that would be a thing of the past, but now Verizon Wireless is going on the record claiming that won’t be the case after all.

PCMag.com is reporting that Verizon Wireless customers still won’t be able to unlock their handset and jump over to rival AT&T when their LTE network launches -- or vice versa. Despite using SIM cards like other GSM devices, Verizon’s LTE network will remain incompatible.

According to Verizon spokeswoman Brenda Raney, their handsets will not “be compatible on other LTE networks in the U.S.” because “the phones will be on different frequencies.”

Both Verizon and AT&T are running their LTE networks in the 700MHz band, but the trouble comes with exactly where that spectrum lies. In the case of Verizon, their network is “mostly in 746-787MHz, while AT&T’s will be primarily in 704-746MHz.” There is a small amount of overlap in an area called “lower B block,” but the website claims it’s “not much.”

For AT&T’s part, it’s unknown at this time if any of their devices may possibly roam on Verizon’s LTE network, since the company has yet to roll out any such handsets. For now, this could rule out a single iPhone capable of running LTE on both carriers, although Apple isn’t expected to adopt the high-speed technology until 2012 at the earliest anyway.

Of course, there’s nothing stopping either carrier from implementing handsets that use each others’ bandwidth spectrum -- but apparently, Verizon is simply choosing not to. This means the two biggest U.S. carriers in the United States will likely remain incompatible with each for the foreseeable future, just when we thought LTE might finally unite them.

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