VOIP Packet Loss / Jitter

I am currently running Fortinet 5.44 on a 100D firewall.  Just recently some users started to complain about poor quality of phone calls.   I started a wireshark on the VOIP vlan and ran RTP Stream analyzer on 30 mins of data that I collected.   From looking at the results I have some packet loss and jitter coming from my local SIP provider into phone server. Looking at the outgoing stream from the phone server to the SIP provider I am not loosing no packets or have any jitter.  

My firewall is connected on a 1GB fiber Internet connect.    

I thought a policy shapper might help and I see no data being collected.  

I am open to any ideas. 

Thanks,

Richard