If you find that you have a commandButton or link that does not seem to be calling the class method you have defined in the action attribute, you may find that it is because the form is trying to validate itself before sending the request, even if you are only re-rendering a few components.
The solution is to use the attribute immediate in the commandButton element, eg:
<apex:commandButton value="change" id="changeAccount" action="{!testAction}" immediate="true" rerender="log" Status="status" />
