0x11bytes wrotetry this at home:
- turn off 3G
- use wifi
- block port 5223
- check if whatsapp still works.
mtc probably opens only port 5223/TCP with that bundle.
Did you try the above?
If it is a matter of blocking a port, then in theory we can setup a server to listen on that port, send requests to that server, the server then converts the requests to port 80 sends them on our behalf, then reply to us back on port 5223...I think