More likely that they are blocking most ports which would be more sensible. Have you tried common ports such as 80, 443, 8080 and so on?
A public VPN service is unlikely to help you with this issue as they are also unlikely to allow any inbound access. Though for a different reason. That it is difficult for them to ensure correct routing of traffic and hard to maintain security.
However, if you set up your own VPN, you can certainly then do what you want.
Find a VPS (Virtual Private Server) provider that allows private VPN use (many don't) and set up OpenVPN on there.
The open ports on a VPN come from the other end of the connection. E.g. on the network running the VPN service.
The ports that your ISP have open become, therefore, irrelevant other than that you need a single available port to connect to the VPN in the first place.
Your ISP cannot possibly have closed all ports otherwise the connection would be pointless. However, they will have restricted them. As long as you have access to port 443 (the default for HTTPS), there are VPN services you can use.
So you need to check with your VPN supplier what ports they have open.