I used Toronto for awhile then Montreal and then Chicago and it does it on all of them. It's not all the time but it is fairly often. I have my DID on voip.ms set to go to a ring group which only has my cell as a call forward member. I have that because I have 2 DIDs that I send to my cell and by using a ring group I can prepend the caller ID to say L1 or L2 for Line 1 or 2 before the caller ID.
However my employee is connected directly to voip.ms using an IP phone and 9 times out of 10 when I call her, my cell will say "Connected" and the timer starts and i hear silence, then 5 seconds later I'll hear her background noise come on and her being like "Hello????"
Then same with if someone calls my DID and it goes to my cell phone, I'll answer and hear them no problem and they just don't hear me.
I've had numerous customers reporting the same problem to me. VoIP.ms has offered numerous suggestions, none of which have been effective. The important point is that these same customers didn't used to have the problem. I have no doubt that the problem would cease if I were to port the customers to a different provider. That is not my goal, however, at some point the customers are going to become impatient and instruct me to do whatever it takes to permanently resolve the situation.
The problem of of the incoming caller not being able to hear the party who is answering the call at my customer locations only last 2 - 5 seconds and it appears to affect somewhere around 2% of the incoming calls.