"Phone calls"

I'm pregnant with my first child, and I have been having my appointments at BBC, I have had good experiences whilst there. However, whenever I try to call the centre they never pick up! I have an appointment that I need to cancel as I have been in contact with someone who has tested positive for covid, I have been calling for four days and no one is picking up the phone! This is utterly ridiculous, I can't go down there so I don't know how I am supposed to get a hold of them. Why would they not answer the phone, everytime I've been there, there has always been someone at the front desk. This is making me incredibly upset. God forbid it was an emergency with the baby, I would have no way to get a hold of them. Please sort this out.