The method `getAttributeText` looks like this:

    public function getAttributeText($attributeCode)
    {
        return $this->getResource()
            ->getAttribute($attributeCode)
                ->getSource()
                    ->getOptionText($this->getData($attributeCode));
    }

Notice the last 2 lines.  
They mean that the method calls `getOptionText` from the source model class.  
I see that your attribute has a custom source model `npm_recurrex/package_source`. Make sure that model has the method `getOptionText` or it's parent class has it and returns what your need.