A CO by HIMSELF? That is definitely working around the 'rules' of the GB. But I know every country does things differently.
If I was in your husband's shoes [Which I have been with elders and my family myself] I would be really upset that they usurp your husband's headship to talk to you. You can always tell them that they will have to wait and talk to him. That's what NE told the elder's that called a month ago on a conference call. They've left 2 messages since then, but we haven't heard from them since.
Also, if no one applies MT 18 and comes to talk to you, then you have the right to tell them until that person/accuser does then you WILL NOT discuss it and it is NOT a congregation matter!!
That's the biggest problem with MT 18, nobody, especially the elders wants to apply it! The elders could relieve themselves of so much work & problems if they would just tell the blabber mouths that they need to go apply MT 18 before coming to the elders. 99% of the time it would be dropped and the elders could enjoy the time with their family's. But elder's as we all know, LOVE their Ecclesiastical authority!!! So they are willing to sidestep that entire MT 18 policy.
Affectionately Brother of the Hawk [I will surrender my mind no more, forever]