It is totally out of line to harrass someone about volunteering around the complex. You cannot make someone volunteer.
Though you should consider whether your levies will cover a third party. In our complex, when it was built and all moved in, we were all like minded people. At least 50% of us would do a bit of work here and there. Then most of these volunteers move out and left just a few. In their place were owners who expected absolutely everything done for them out of their levies. Problem was, the levies were not calculated to cover everything. So it was put to the owners that we would have to increase the levies, quite substantially if they wanted everything covered. We were met with a resounding “No increase”.
The few in the complex who continued to do a bit of work gave up. We have personally witnessed owners who will step over pieces of paper in the driveway, or at their front doors because that is for someone else to do. So we did get in third parties to do the most of the work. And we did have to increase the levies. I would estimate that our costs in maintaining this complex have risen about $7,000pa because of paying for third parties. And thats with owners/residents expected to keep the immediate area of their units clear, clean and tidy (which many don't) and with a few of us still doing extra work when necessary between visits from the teams we now pay.