Hi Imran,
The quintum A800 can do the prefix screening you wanted. You can define this in the PSTN Trunk Group LAM patterns.
The only external device I can think of that can do prefix screening before it reaches your quintum gateway is a gatekeeper. The Tenor Gatekeeper can do this by configuring static routes.
Or maybe you can ask your traffic source to do the prefix screening for you.
Regards,
Tuckmol