Hello ,
First of all I apologise for my english. I will do my best to explain my problem

I have installed and successfully configured PBX Server which IP is 192.168.0.9. I have several IP phones located in my company and they are working fine.

My external IP address of RB3011 is lets say: 10.10.10.1 ( WAN side ).

I've have a smarthone on which i have configured SIP account with external IP address ( 10.10.10.1 ) and I can call to my company IP phones.
I've also have WLAN covering entire company and while I'm in work my smartphone is connected to that WLAN.

Now, whenever I call from my smartphone to one of the IP phones while at work ( I'm connected to WLAN ) I'm still using external IP address ( 10.10.10.1 ).

My question is , how to redirect/forward packets when calling from my smartphone which is connected to WLAN ( 192.168.60.0/24 network ). to my PBX Server 192.168.0.9 on port 5060 tcp, udp while at work ?

I assume you have a port forward on our router in order to connect you mobile phone via your external IP.
If that is the case you should configure a HairPin NAT rule in order to be able to connect via your WAN ip when inside your network.

The thing is that I do not want to connect ( call ) through my WAN IP and use my internet bandwidth when inside WLAN.
I want packet to get forwarded directly to my PBX server so that they are not going through my WAN port whenever Im inside my LAN.

The thing is that I do not want to connect ( call ) through my WAN IP and use my internet bandwidth when inside WLAN.
I want packet to get forwarded directly to my PBX server so that they are not going through my WAN port whenever Im inside my LAN.

I guess it is just a matter of routing, you don't have to worry about your bandwidth.
When inside and connected to WLAN the traffic will not really be a load to your internet, it just traverses your router over WLAN, WAN interface and back into your inside network.