Disabling SIP ALG on Cisco Router (C891F) running Cisco IOS

Hello everyone!

Sadly I am having some problems disabling SIP ALG & ensuring UDP port 5060 is open and hoping someone here would be kind enough to outline how I am dunce and what to do about it. :)

The steps I took to disable SIP ALG were... (source)

1. I logged into the router via serial console
2. enable
3. configure terminal
4. no ip nat service sip udp port 5060 (it didn't returrn anything)
5. no ip nat service sip tcp port 5060 (this command registered).
   

However, when our VOIP provider ran their diagnostics/tests the 2 issues persisted...

1. An active SIP ALG was detected on our network
2. UDP port 5060 is blocked

It may be worth mentioning that I did not set up this router and my experience with Cisco CLI / IOS is limited.