If your ISP is blocking the standard VoIP ports, the only work arounds I know of are:
1) Something like Skype will often work, as Skype "port hops" to hide that it's a VoIP application. Skype does have several other "down sides", but it is better able to get around "port restrictions" than most of the other services.
2) If you have access to a VPN "Virtual Private Network" server in an "unrestricted" area, you can VPN (assuming your ISP doesn't block VPN) to that server, and do your VoIP from their internet (via the VPN). Since VPNs are encrypted, it will just look (to your ISP) as if you are doing some encrypted traffic remotely.
3) If you have a friend with an IP-PBX (in an area that doesn't restrict ports), you can ask your friend to let you use their PBX via non-standard VoIP ports. But as soon as the ISP catches wind of this (and it can easily show up in their "traffic logs"), they can take action to shut this arrangement down.
4) Or, you could give up using the ISP totally, and go with some other option for "cheap calling". For example, you can use the "Web Call" feature of
http://www.voxalot.com to connect two VoIP calls togeather WITHOUT using any VoIP equipment on your end. If you were willing to pay VoIP rates to call your local phone, you could then use "Web Call" to call your phone and also the VoIP location of your choice. Voila, VoIP rates using your normal phone. Of course, the "down side" is that you will be paying (VoIP rates) to call your phone, in addition to whatever you are paying (if anything) for the number you are trying to reach. And your ISP could always block access to the VoXaLot web site (but you could use an http proxy to get around that block).
NOTE: Because of the slightly strange way that VBuzzer does things, VBuzzer is currently one of the few BYOD providers that will NOT work with VoXaLot's "Web Call".