Keep losing our Static IP

A tech came out yesterday, checked our wires / signals and plugged his laptop into our Comcast gateway and did a firmware upgrade - said our gateway was working fine.  In doing so, some of my port forwarding was change and we LOST our static IP address (we've had this address for 13+ years) which took down our external website, email and remote VPN access.  This is the second time this has happened.  The call center people (India?) were not able to fix this issue as it appears to be something in the switches @ comcast and nothing to do with our equipment.  This is the second time this has happened.  How do we keep this from happening?  We called the tech out because our Internet service kept going intermittently up and down for the past few weeks.