Cisco :: PIX 525 Firewall / Voice Network Not Working After Data Network Migrated

My company have a Cisco PIX 525 firewall which is cater for NOC internal data network and also voice network, the subnet for data network is 192.168.2.0/24 and the subnet for voice network is 172.16.2.0/24. someday this NOC firewall was faulty. I was migrated the data network from this NOC firewall to the other temporary firewall just at the moment. And the voice network i migrated it from where it orginal at NOC firewall to a VOIP system which actually having a connection with my temporary firewall(This temporary FW only to take the traffic of data network). After the migration of data network from old firewall to temporary firewall and also the migration of voice network from old firewall to PABX system. The subnet for data network remain the same as 192.168.2.0/24, but the subnet of voice network i edit from 172.16.2.0/24 to 192.168. 3.0/24.Now when i want to use one Cisco router 2600 to replace this temporary firewall then facing problem at the voice network....The data network after migrated from temporary firewall to new 2600 is ok, users can browsing. But when i trying to at the same time when the data network been migrated , it will affect the voice network which still located at PABX. ..user cannot make call...I was thinking reason because this voice network which currently in 192.168.3.0/24 is tight to somewhere on the 192.168.x.x at the old firewall internetwork. So, when i migrated the data network over to new router, it will also cause the failure of voice even thought after i migrated the voice system to new router.So when i do the disaster recovery back to the temporary firewall for both data and voice. The voice is resuming to normal.