How do I escalate a serious issue with Comcast?

In the middle of the night - about 2:30 am,  a VPN tunnel of ours went down. When I contacted customer service I was told that they don't troubleshoot vpn issues and that there was no way to talk to anyone else or to escalate the issue to anyone else. This tunnel is used to access a major corporation and after contacting the corporation I learned that this issue is affecting all Comcast customers who are accessing their systems but none with other providers, but I've not been able to get any help from Comcast.

Comcast customer service told me that all they could do is send out a tech to check and replace our modem. We've investigated further and it looks like Comcast is blocking UDP port 50 needed by the VPN but I can get no help from Comcast - how do I get around this? This is a major issue affecting our ability to perform work according to our contracts. Surely there must be a way to get Comcast to look into this. It's not a trivial issue for us to switch ISPs, since we have dedicated IPs and multiple servers & domains that would need to be reconfigured but if we can't get this resolved we'll need to.

Any help would be greatly appreciated