Internet Banking Security?

Recently I rang my internet bank of 10 years for a routine enquiry. Nothing technical or hard in the slightest

During the second password letter of security, their phone system cut me off. I rang back 2 minutes later, and was told my account access had been suspended, and I had to go through extra security because of it

This meant they refused to speak to me until I rang on a number they recognised. They didn't have my mobile number on file so they couldn't ring this back. They wouldn't accept the work extension I was using, because we've changed networks from BT landlines to Cisco network phones (which meant the number was the same except for 3 digits)

At least (can't be bothered counting) 5 calls later, I took the afternoon off and went home to ring from a landline to adhere to this hideous procedure. The password I have been using was then refused, to which I had to go through the same security questions again. I changed the password to the one I've used 10 years previous

I rang again 3 days later because I'd calmed down. The letters of the password failed again, and I've changed the password to the same password I changed 3 days previous, to the same password I've always had with them

My question is, does a phone line accidently cutting out at their end, satisfy the reasonable excuse that there's been a security breach?

I was told scammers and fraudsters have very clever ways of making money, and that my phone call cutting out could very well be part of this

Have I got a case to complain about being poorly treated? Should I be angry that I was refused service because their phone system failed?