I run and operate an ISP in Los Angeles. I know all aspects of CISCO. Including QOS, MPLS, VPN (IPSEC or GRE), BGP. Most customers with multiple sites either have MPLS with BGP or VPN. Both offer challenges to VOIP due to Jitter caused by poor QOS. I can create QOS profiles that will optimize your voice over these networks. We can allocate bandwidth to queues and proritize your traffic. I do this regularly for large customers as a consultant. I know how to work with large ISP such as Masergy, Telepacific, AT&T, Global Crossing, and of course my own.
I also understand PCI compliance and how to provide a solution that will satisfy the compliance issue by providing SIP to PRI trunk. When you are connected via PRI, it doesnt have the encryption requirement that is needed when using SIP by PCI compliance.
1-2 hours on the phone will convince you that I can help you. I can also work on a monthly retainer which may save you money in the long run.