Help with WISP Router

Dear everyone!

We are desperate! We have an WISP and everything works perfectly except for VoIP. We use WiMax Equipment, with WiFi and local connections, all of this at the end is tied to the RV016 Router.

The router has the latest firmware and pretty much does its job [We don't use DMZ or any VPN] but when it comes to local clients or wireless clients using VoIP, nothing goes through. I believe that this is because of the load balancing. I have created rules, followed the Bandwidth Management Configuration Guide and more, but when the problem is fixed, the wireless part of our network is affected[Wireless portion managed by Meraki]. I do not know how this could happen if the firewall rules shouldn't have any effect on the wireless radios and their coverage areas. It seems unlogical to me. As the manager for the network and engineer, I have no idea what's going on and what I could do to solve it.
If VoIP works [via Firewall Rules and Bandwidth Management] the coverage area is affected, and if it doesn't, our clients can't use VoIP. And as I mentioned before, there is no logical relation between one affecting the other...

What can I do? Any suggetions are welcome! I have been trying to fix this problem since last December...

Thanks,

Faruk Muhti