[CentOS] [OT] DNS - asking for your opinion

Hi list, I first apologise because this is really off topic, but I would 
really appreciate your opinion on this.

I have had a very hard time configuring a DNS server to answer reverse 
dns queries, and I would like to have your opinion on my provider 
behaviour.
We have 3 classless subnets and asked the provider to delegate reverse 
dns. They configured their server and emailed me all was fine but i it 
didn't work for one subnet, so I mailed back and they assure their side 
was all perfectly configured.
I finally find out (spending lot of time and thanks to www.dnsstuff.com) 
that they configured 2 zones like 128/27.x.x.x.in-addr.arpa and one as 
128-27.x.x.x.in-addr.arpa, so my server was not able to answer queries 
because I had all zones 128/27.x.x.x.in-addr.arpa.
As said before it is my first time configuring Bind and I am sure the 
more experienced would have notice and solved it quite soon, but still I 
wonder why to use different convention (without telling us) and even if 
this is correct (red the http://rfc.net/rfc2317.html and they always use 
"/" not "-"  ).
Hope I won't be banned from the list for this email......

Thanks for your time reading this

Simone