Here’s a little bar graph that didn’t make it into ChangeWave Research’s Aug. 4 report about customer satisfaction with the iPhone 4.

Asked how likely they would be to switch carriers if Apple (AAPL) made an iPhone for Verizon (VZ), 18% chose “somewhat likely” and 13% “very likely.”

And this is from respondents who already own an iPhone. Complaints about AT&T (T) were the No. 1 and No. 2 things iPhone 4 owners said they disliked about the device in the Aug. 4 survey. See here.

Rumors of a Verizon iPhone, which have been kicking around for years, have heated up in recent weeks, with speculation centered around January 2011.

UPDATE: A Morpace Omnibus Report based on a survey of 1,000 consumers July 15-20 got similar results. See their bar graph below.

See also:

• Verizon iPhone: A plausible timeline
• iPhone 4 survey: 17% fewer dropped calls than iPhone 3GS

[Follow Philip Elmer-DeWitt on Twitter @philiped]