Oh my goodness, what a position they’ve put you in! As Jasmine suggested, if you can switch to an accessible bank, that’s always an option.
Do you have a smartphone? Most banks have a banking app now, with instant chat available. I’ve got both Natwest and Moneybox, and have found their live chat features really useful. If they can’t reply right away, you get a notification text when they have managed to get around to your query. The Natwest one is a little bit annoying as you have to go through the AI bot for a few questions first, but if you type in something like ‘speak to customer service’ it usually cuts to the live chat.
It may also be worth considering – if it’s financially suitable to do so – adding your mum to your accounts if you can. That way, she can go to the bank on your behalf or call up as a joint account holder and manage the account for you.
Let us know how you get on – and, as Jasmine mentioned, if we can reach out to your bank on your behalf.