I have but one simple request: stop using VMs over PMs (unless your opponent's inbox is full)
PMs force pop-ups, meaning they are harder to miss.
PMs have read receipts, meaning you can know with certainty that your opponent read the PM and ignored it.
VMs are easier to miss a response to, considering if someone responds to your VM on their own wall (which is not unheard of), you don't get ANY kind of alert that they responded to you.
In summation: stop using VMs to get in touch with your opponent. Use a PM ffs.