Piwik API returns empty result when period is other than day (no replies)

Hi,

I'm trying to download customer activity data (customer name is saved in custom variable 2) using Piwik API

https://xxx/piwik/index.php?token_auth=xxx&format=xml&date=yesterday&period=day&idSite=3&module=API&method=CustomVariables.getCustomVariablesValuesFromNameId&idSubtable=2&segment=customVariableValue2==CompanyName

Code above works well, but whenever I try to change period to week, month or something different than day, result is:

<result/>

Any tips?