Tech Prefix errors

I am using a tech prefix when sending calls out my PBX to a billing system. For some reason, instead of putting the # sign after the prefix, it is putting %23 in it’s place. Below is sample from sip debug. Has anyone ever seen that before?

To: sip:12520%[email protected]:5060

In my trunk settings, I put 12520# in the “Tech Prefix” area.

Any help is appreciated.