my SIP baed Internet phone is stop working

hi all,

It would be great if someone give me an insight of this problem. Two days ago, Signaling/Registration of phone were failed. I thought Verizon might apply some Access-list rules for SIP related traffic. i try to change port fowording/dmz and all other stuff. but so far no luck.

So, My question is that does Verizon really decide to block SIP traffic??? this is real pain.

Could you anyone know how to make this work, please share something for me.

Btw, how to check port connectivity for UDP 5060, 20000-60000?

thanks