Having issues dialing queue numbers that have 4 digits

I have setup two queues with the numbers 1345 and 1999. I can pick up any phone and dial these numbers and I will get connected to the appropriate queue. I then setup a queue with the number 8001. When I try to dial 8001, the phone only dials 800 and then tells me that the call cannot be completed as dialed (since the extension 800 does not exist). It seems that the system is only recognizing the first three digits and ignoring the last digit for any extension number higher then 1999. Is there a setting where a mask is applied to extension numbers when you dial them? I am new to all this and just inherited the setup/administration duties on our new Asterisk server. Any help would be appreciated. Thanks!

I have not seen anything about a max number of digits or a mask.

How do you know that it only dials 800?

Try monitoring what happens using
tail -f --line=500 /var/log/asterisk/full

Although I can’t remember when or where I saw it, It may go back as far as early versions of AMP. But it pops into my head that there was a restriction on extensions possibly beginning with 800. Again, don’t shoot me if I’m wrong, but it’s something that pops into my head dating back to the early days of asterisk (2004-2005).