Thank you for the previous answers.
Here to ask again
If a person dials a number very slowly the system says
"your call cannot be completed as dialed. please check the number and dial again"
these two happens in the two FXS ports of the pci card
Is there any settings i can try? (time out or something similar?)
thank you
Also please
if the other party is busy to hear the busy tone and not the above message again
The phone company does exactly the same thing. If you take too long to dial a number, you’ll get that exact message.
As to hearing a busy signal instead of a message, I remember reading something here from a couple of weeks ago about someone that wanted “old fashioned” call notifications. Search the forum for “busy signal” and see if you can find it.
See
https://wiki.asterisk.org/wiki/display/AST/Function_TIMEOUT
More generally google asterisk timeout(digit)
The default is 5 seconds, so maybe your clients need some Amphetamine 
It is also possible that you have your digit timeout set too low on your physical/virtual phones, but that is something only you can correct as each variety will do it differently.