Configured a PJSIP trunk on UDP, managed to get a few calls across but then were asked to switch to TCP (all other settings remaining the same), so I changed the trunks transport accordingly.
But the trunk still reacts to UDP inbound calls?
Is this because of “Allow Transport Reload” being on NO? If yes, does this mean I actually have to restart Asterisk to have the trunk changed from UDP to TCP?
There is no restriction on what transport (UDP or TCP) incoming traffic is handled by for anything. If UDP is configured as a transport on the system, then it will accept traffic. Turning off UDP (if FreePBX allows it) would require restarting Asterisk.