How to Fob Off Your (soon-to-be-ex) Customer with Nonsense

How obstructive can "support" get? Our NGO changed treasurer and I asked them to change to addressing their emails to "Treasurer" instead of using the name of the previous Treasurer. No change of email address needed. Would they do it? No, I must email them from the registered email address, which was that of the Treasurer. I did. So they send me the same request again. I think we should move to a different company.