Hi,
what type of ATA you are using, may be ATA is not forwarding digits to voxalot. There can be internal dialplan for your ATA as well. Try to use any Softphone like
CounterPath Corporation | Home. Check if you can reach voxalot or not. I use 000600 to test echo & my dial plan is like as follows:
Pattern*= _000600
Replacement= *${EXTEN:3}
Provider=voxalot
Then I dial 000600 from my phone to test echo.
Regards.
majo