the recommendation is 150 ms of one way delay, depending on the scenario up to 400 ms might be acceptable.
was the ping tested using the voice values??? because otherwise if you have QoS configured the ping was not treated as such and only as ICMP traffic and it's useless as the values do not reflect the real delay for voice
check the BW and QoS settings, ask your link provider if they could provide a higher SLA for voice traffic. the real only way to find out if the quality is going to be really bad would be to make a test call.
HTH
java
if this helps, please rate
HTH
java
if this helps, please rate