This will not work, sorry.Port forward 10000:20000 to 9000:9225
That may be suspicious to provider. Imagine that ATA from provider is using that (first) range. We really need per trunk port range override?You don't need to adjust anything.
Provider may use UDP ports 10000-20000 (probably an Asterisk), your 3CX PBX -- 9000-9255.
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.