Best thing to do is to call them being polite ( although I’m sure you are anyway) and calmly tell them the situation, I know as previously working in Customer Service for some years, if a person phoned with all guns blazing, same as face to face, then immediately my hackles would rise , if you get someone that you feel isn’t giving it the attention it deserves then ask to speak to a manager, you may get ‘all our managers are busy right now, ‘politely say ‘ I’ll wait
Good luck x